If you are moving abroad, taking an extended break from a device, or simply pausing a second line you use irregularly, the default outcome is straightforward: do nothing, and the number eventually disappears. Most carriers reclaim inactive numbers and reassign them to new subscribers. Once reassigned, a number cannot be recovered.
There are five practical ways to prevent that: stay on the cheapest available plan, keep the number on an eSIM or secondary line, port to a low-cost prepaid or MVNO, use a carrier suspension service if one is offered, or move the number to a VoIP service. Each approach has a different cost profile, reachability level, and level of effort. This guide explains how each works and when to choose it.
Why Phone Numbers Get Reclaimed
Phone numbers are a finite resource, allocated to carriers by national numbering authorities under the ITU-T E.164 framework. Carriers are required to return numbers they are not actively using to ensure the pool does not run dry. When your account closes — or when a prepaid SIM goes inactive long enough — the carrier treats the number as unused and eventually makes it available to a new subscriber.
The reclamation timeline is not standardised. In the United States, regulations set a minimum of 45 days before reassignment, though carriers often wait longer; timelines differ significantly in other countries. Carriers do not typically notify you before reassignment begins.
The practical consequence is that any service you have registered to that number — SMS two-factor authentication for banking, accounts, or messaging — will send codes to a stranger after reassignment. This is both a continuity problem and a security risk. Maintaining an active account that holds the number is the only reliable way to prevent it.
Option 1: Downgrade to the Cheapest Available Plan
The simplest approach to holding a number is to stay with your current carrier on the lowest-cost plan available. Rather than cancelling, you change to a minimal plan — often a low-data or voice-only tier — and pay the reduced monthly cost to keep the line active.
When This Makes Sense
- You want minimal setup effort and no change of carrier.
- You may return to heavier usage within a predictable timeframe.
- Your current carrier offers a meaningful step-down in price.
- You want the number to remain fully reachable (calls, texts, data) during the hold period.
Trade-offs
A downgraded plan keeps your number on the same carrier with the same number reachability it always had. Inbound calls and SMS arrive normally; eSIM profiles and device settings remain unchanged.
The cost depends entirely on what your carrier offers at the low end. Some carriers offer significant reductions; others do not have a meaningful low tier — they offer only their standard plans or nothing. If the cheapest available plan still represents a significant monthly cost for a number you may not use at all, one of the other approaches below is worth considering.
Check your contract terms before downgrading. Some carriers impose a plan-change fee or require you to remain on a new plan for a minimum period. If you are within a minimum-term commitment on your current plan, early plan changes may trigger penalties.
A useful reference point: many carriers also offer a formal suspension service (covered in Option 4 below) that is cheaper than their cheapest active plan. Check both options before deciding.
Option 2: Keep the Number on an eSIM or Secondary Line
If you already have a dual-SIM capable device, keeping a number as a secondary eSIM alongside a primary SIM is one of the most flexible approaches. The number stays active on its original carrier, the eSIM profile remains installed on the device, and you can receive calls or texts on that number whenever the eSIM is enabled.
How eSIM Retention Works
An eSIM profile is a software credential stored on your device’s eUICC (embedded Universal Integrated Circuit Card) chip. Once installed, it persists on the device even when the line is disabled — you do not need to download it again when you re-enable the line. The profile corresponds to a real active account on the carrier’s network, so the number remains registered and reachable as long as the account stays in good standing.
You can disable the eSIM line in Settings when you do not want it to consume data or battery, and re-enable it when you need to receive calls or check messages. Switching takes seconds.
Limitations to Understand
An eSIM profile is tied to the device on which it was activated. If you replace your phone, you will need to re-provision the eSIM on the new device by contacting the carrier. Most carriers support this online, but some require a support request.
eSIM profiles can also be deleted accidentally during a device reset or software restoration. Before performing a factory reset or major OS migration, confirm whether your eSIM profile will survive or whether you need to re-download it first. On iPhone, iOS 16 and later provide an option to back up and transfer eSIM profiles to a new device, but only during a device-to-device transfer — not from a backup restore.
The secondary line still needs to be on an active plan with some cost. The goal is to choose the cheapest plan the carrier offers for that secondary line, not to avoid cost entirely.
Option 3: Port the Number to a Low-Cost Prepaid or MVNO
Mobile Number Portability (MNP) lets you transfer a number from one carrier to another while keeping the number unchanged. Porting to a carrier with a cheaper entry-level plan or pay-as-you-go option reduces the holding cost, often substantially.
Why an MVNO or Prepaid Carrier Can Be Cheaper
MVNOs lease capacity from MNOs and resell it, often at lower prices for low-usage or no-frills tiers. For holding a number without significant usage, the specific data speed and coverage tier matter less — what matters is cost and whether the account can remain active with minimal activity.
Pay-as-you-go prepaid options are especially relevant here: you pay only when you actually use the number. If months pass without a call or text, you pay only what is necessary to prevent the SIM from deactivating (see the caveat about minimum activity below).
The Port Process
Porting requires a transfer credential from your current carrier (a PAC code in the UK, a Number Transfer PIN in the US, a RIO code in France, and similar credentials in other markets) and a new account opened at the receiving carrier. In most countries with mandated MNP, the process completes within one working day for a simple consumer port, and porting is free of charge. See the MNP guide for country-specific steps.
Once ported, the number lives on the new carrier. Any calls or texts sent to that number route to the new carrier’s network.
Minimum Activity Requirements on Prepaid Plans
Most prepaid plans require at least one qualifying activity — a call, text, data session, or top-up — within a rolling window, typically ranging from 60 days to 12 months depending on the carrier, to keep the line active. If the window passes with no activity, the SIM deactivates and the number enters the reclamation queue.
Before porting to a prepaid carrier for number holding, confirm:
- What counts as qualifying activity (some plans require a purchase, not just network usage).
- How long the activity window is.
- Whether there is a minimum balance required to keep the account open.
- Whether the number can be ported out again later if you want to return to a full-service carrier.
Option 4: Use a Number Parking or Suspension Service
Some carriers offer a formal account suspension or number-hold service. Under this arrangement, the number remains registered in the carrier’s system — not in the active number pool — but the account is not fully active. Monthly cost is typically lower than the cheapest active plan, and sometimes nominal.
Where Number Parking Exists
Carrier-level suspension services are not universal. Their availability, cost, and duration limits vary by carrier and country.
United Kingdom: Some UK carriers offer account suspension for documented reasons (travel, medical grounds). The terms vary by carrier, and most have duration limits.
Australia: Some Australian carriers may offer temporary account suspension on request — terms vary and should be confirmed directly with the carrier.
Japan: au (KDDI) offers a temporary suspension service specifically designed for subscribers living or travelling abroad (up to 5 years). The number is preserved while the account is suspended, and service can be reactivated on return. Other Japanese carriers have their own suspension programs with varying terms.
United States: No major carrier offers a standardised number-parking product for the general public. Verizon, AT&T, and T-Mobile offer military deployment suspensions, which pause billing for active-duty members. Outside of military status, the closest US equivalent is moving the line to the lowest available plan, or porting the number to a VoIP service. Some carriers also allow a temporary suspension for documented medical situations, but these are case-by-case and not universally available.
Germany and EU: Under the European Electronic Communications Code (Directive 2018/1972), subscribers retain number portability rights regardless of account status, but no standardised suspension product exists at the EU regulatory level. Individual carriers in Germany and other EU countries may offer voluntary suspension programs.
What to Verify Before Using a Suspension Service
- Maximum suspension duration (most carriers cap it at 90 days, 6 months, or 12 months).
- Whether the number can be ported out during or after the suspension.
- Whether the suspension renews automatically or requires manual extension.
- Cost during suspension (sometimes a nominal fee, sometimes zero).
- What happens at the end of the suspension period if you do not act — does the account return to a standard plan automatically, or does it cancel?
Contact your carrier’s customer service directly to confirm current suspension terms. Published terms on carrier websites for these programs may not be updated frequently.
Option 5: Port the Number to a VoIP Service
Porting a number to a Voice over IP (VoIP) service transfers it out of the mobile carrier network entirely and places it on an internet-based voice infrastructure. The number remains yours, inbound calls and texts arrive via the VoIP app, and the cost is typically lower than maintaining a mobile plan.
How VoIP Number Holding Works
VoIP providers that accept mobile number ports — such as Google Voice in the United States, or similar services in other markets — take over the number through the same MNP process used for carrier-to-carrier ports. Once ported, inbound calls arrive through the VoIP app on any internet-connected device. SMS messages can be received through the app interface.
Because the number is no longer on a mobile carrier’s network, it does not require a SIM card, an eSIM profile, or any hardware. The account stays active as long as you maintain the VoIP service.
Trade-offs and Limitations
SMS OTP compatibility: Some financial institutions, banks, and online services restrict SMS-based one-time password delivery to numbers registered on carrier networks, and block or fail to deliver to numbers identified as VoIP or landline. If any of your accounts require SMS OTP delivery, test delivery to the VoIP number before fully committing to this approach. Alternatively, migrate those accounts to authenticator-app-based two-factor authentication before porting.
Outbound calling: Outbound calls from a VoIP number may display as “Unknown” or show a different caller ID on some recipients’ phones, depending on the VoIP provider and the recipient’s carrier.
Emergency calls: VoIP numbers may have limited or no emergency services (911 in the US, 999 in the UK, 112 in the EU) connectivity compared to mobile carrier lines. Do not rely on a VoIP-only number as your primary contact for emergency situations.
Portability back to mobile: VoIP numbers are generally portable back to a mobile carrier under MNP rules, but this depends on whether the VoIP provider supports port-out requests. Confirm port-out support before committing to a VoIP holding strategy, especially if you plan to return the number to a carrier at some point.
Geographic restrictions: VoIP number porting is available in some countries (notably the US, UK, Canada, and Australia) but not universally. In countries without regulated VoIP number portability, this option may not be available.
Comparing the Five Approaches
The right choice depends on three factors: how long you need to hold the number, whether you need it to be reachable in real time, and what cost is acceptable.
| Approach | Reachability | Minimum Ongoing Cost | Best For |
|---|---|---|---|
| Downgrade to cheapest plan | Full (calls, SMS, data) | Low monthly fee | Short to medium holds; same carrier preferred |
| eSIM / secondary line | Full when enabled | Low monthly fee | Device already supports dual eSIM; flexible enable/disable |
| Port to prepaid / MVNO | Full | Pay-as-you-go or low monthly | Long holds; cost reduction is the priority |
| Carrier suspension service | None or limited | Nominal or zero | Short holds where carrier offers the service |
| Port to VoIP | Inbound via app; no mobile SMS | Low or zero | Number rarely used; no SMS OTP dependency |
No approach is cost-free: maintaining any number on any platform requires some ongoing engagement, whether a monthly fee, a periodic minimum usage event, or a subscription to a VoIP service.
The SMS Two-Factor Authentication Dependency
Across all five approaches, the most practically important question is whether any of your accounts send SMS-based one-time passwords to the number you are holding.
If yes, and you let the number expire or port it to a VoIP service that those accounts do not recognise, you may lose access to those accounts entirely — or the codes may be delivered to whoever eventually receives the reassigned number.
Before pausing, suspending, or porting a number:
- Identify every account that uses this number for SMS OTP.
- For each account: either update the SMS OTP to a different number you are keeping active, or migrate to an authenticator app where the service allows it.
- For accounts that only support SMS OTP and cannot be updated easily (some financial institutions), ensure the number remains reachable throughout the hold period.
The SIM swap fraud guide covers the broader security implications of SMS OTP dependency on mobile numbers and why authenticator apps are preferable for sensitive accounts.
eSIM Retention When Changing Devices
If you are holding a number on an eSIM and plan to change your device during the hold period, understand that the eSIM profile does not automatically transfer.
Steps to preserve the eSIM when switching devices:
- Before resetting or surrendering the old device, confirm whether your carrier supports eSIM transfer online or requires a support request.
- On iPhone, use the direct device-to-device transfer (Quick Start) method — iOS 16 and later support eSIM transfer during this process. A restore from iCloud backup does not transfer eSIM profiles.
- On Android, contact the carrier to re-issue the eSIM profile to the new device. The process varies by carrier but typically involves logging into your account and selecting the new device.
- After setting up the new device, verify that the held eSIM line appears in Settings and that the number is still active.
If you are holding a number for an extended period without actively using the device it is on, consider whether porting to a low-cost prepaid SIM on a physical card — or to a VoIP service — simplifies the situation, since those approaches are device-agnostic.
Choosing an Approach by Situation
Moving abroad for six months or less: If your current carrier offers a suspension service, that is the simplest option. If not, downgrade to the cheapest active plan or port to a pay-as-you-go prepaid at home.
Moving abroad indefinitely: Port the number to a VoIP service or to a pay-as-you-go prepaid that a trusted contact can maintain if needed. Assess SMS OTP dependencies before acting.
Pausing a second line you use infrequently: Keep it on a low-cost prepaid with minimal monthly or periodic cost — or consider a dedicated sub-line designed for exactly this purpose. eSIM works well here if the device supports it — the line can be disabled when not needed and re-enabled in seconds.
Preserving a number for eventual return: Port to a low-cost prepaid or MVNO. Confirm that MNP port-out is available from that carrier when you eventually want to return the number to full service.
Number with significant SMS OTP registrations: Do not port to VoIP until you have audited and migrated or updated all dependent accounts. A downgrade or suspension service that keeps the number on the mobile network is safer in this case.
FAQ
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Can a carrier refuse to let me port my number to a prepaid plan or VoIP service?
In markets with mandated MNP — including the US, UK, Australia, EU member states, Canada, and Japan — carriers generally cannot refuse a valid port request on the basis of account type or destination. They can reject a port if the account credentials do not match or if there is an active account lock. Outstanding contract balances or early termination fees are still owed after the port completes, but the balance cannot be used to block the port itself. See the MNP guide for country-specific details on port refusal and escalation to regulators.
How do I know when a prepaid SIM is about to deactivate?
Most carriers send an SMS reminder before the activity window closes, but this is not universal and some carriers do not send any warning. Do not rely on reminder messages alone. Instead, record the carrier’s expiry policy in a calendar application and set a recurring reminder to trigger a qualifying usage event (a call, a text, a small data session, or a top-up, depending on what the carrier requires) well before the deadline.
If my number gets reassigned to someone else, can I get it back?
Generally no. Once a number has been reassigned and the new subscriber’s account is established, the original holder has no recourse through normal carrier processes. Some carriers maintain a grace period after reclamation before the number is actively reassigned, but this period is not standardised and carriers do not advertise it. Attempting to port a number that has already been reassigned will fail because the account credentials no longer match. If the number was associated with critical accounts, contact those services immediately to update or disable the SMS OTP linked to that number.
Does keeping a number on a prepaid SIM affect its portability later?
No — MNP applies regardless of whether a number is held on a prepaid or postpaid account. When you want to port the number back to a full-service carrier, you initiate the port through the new carrier, provide the transfer credential from the prepaid carrier, and the port completes normally. Some prepaid carriers impose a minimum account age before allowing port-out (typically 30–90 days from activation), so if you have recently ported in, there may be a brief waiting period before you can port out again. Check the specific carrier’s port-out terms when setting up the holding arrangement.
Related Guides
- Mobile Number Portability (MNP) Explained — How MNP works, country-specific steps, and what to prepare before initiating a port.
- Backup Line: Adding a Second SIM for Outage Resilience — How to set up a low-cost secondary SIM for network redundancy and SMS 2FA continuity.
- Using Dual SIM for Travel — Running a home SIM alongside a travel eSIM, with line assignment and SMS 2FA strategy.
- Contract Terms: Lock-In, Termination Fees, and Setup Costs — How minimum-term commitments and early-termination fees affect your options when pausing a plan.
- SIM Swap Fraud: How It Works and How to Protect Yourself — The security implications of SMS OTP dependency and how to protect accounts tied to a number you are holding.