Switching guide
You do not need to cancel your old mobile service first. To keep a UK number, text PAC to 65075, then give the code to the new provider. It will arrange the transfer and close the old service as part of the switch.
The avoidable problems are cancelling too early, using STAC when the number matters, letting a PAC expire, assuming a temporary eSIM number is permanent, or overlooking an early termination charge.
Start here
Use PAC, not STAC, when you want to keep the existing number.
Check signal where you live, work, commute and travel regularly. A cheaper plan is not much use if the network is weak where you need it.
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You can request a PAC while still in contract, but that does not make leaving free. Ofcom says the current provider must include information such as any early termination charge or pay-as-you-go credit when it returns the code. Consider whether switching now, waiting for the minimum term to end or changing plan with the same provider is better.
Use PAC if the number matters. STAC is the clean route when you want to leave but deliberately start with a new number.
Simple timeline
Ofcom says a new provider must complete a standard switch within one working day after receiving a valid code. Provider cut-off times and non-working days can affect when that window starts.
The new provider may give you a physical SIM, eSIM or temporary number. A temporary number is normal: it can appear in phone settings, the provider app or an activation email until the PAC transfer completes.
With eSIM, download and activate the new mobile plan, then submit the PAC when the provider asks. Do not delete a working eSIM just because the old number has not appeared yet.
The new provider receives the PAC and carries out the transfer. It may ask for the PAC, number to keep, temporary number and account or SIM details. Check every digit carefully. Do not send the PAC back to the old provider.
Until the transfer takes place, the old SIM or eSIM may still receive calls and texts while the new service works on a temporary number. On porting day, calls, texts or data can be briefly inconsistent while the number moves. Do not cancel anything manually in the middle of the process unless the provider tells you to.
Timing check
| Your situation | Lower-risk approach |
|---|---|
| You need the phone for weekday work | Submit the PAC ahead of a lower-risk day and avoid critical meetings. |
| You are travelling tomorrow | Avoid starting a number port immediately before travel unless it is necessary. |
| You need banking or 2FA SMS today | Finish important authentication before the porting window. |
| You have both old and new phones | Keep both charged until the number is fully working on the new service. |
This is practical guidance, not a guarantee of a provider’s switching time.
The old SIM loses service and the new SIM or eSIM begins using the transferred number. Restart the phone or toggle airplane mode if necessary, then test an outgoing call, incoming call, outgoing SMS, incoming SMS, mobile data and voicemail.
If calls work but texts do not, or the phone still displays a temporary number, restart it and allow a little time for network systems to update. If the issue continues, contact the new provider first; it is receiving the number.
Ofcom says a new provider must complete a standard switch within one working day after it receives a valid code. A late request, provider cut-off time, weekend or bank holiday can move the practical schedule. Avoid planning a port immediately before a flight, critical work call or banking deadline.
A PAC moves the number; it does not erase money still owed. A fixed-term early termination charge, handset finance, unpaid bill or another service on the account can remain. Review the final bill. Moving one line does not automatically end other family lines, watch plans or broadband.
Changing a number can affect account recovery and SMS two-factor authentication across many services.
Keeping the same number normally means WhatsApp remains associated with it. Banking apps stay on the phone, but avoid a port just before a time-critical SMS verification. Before switching, make sure recovery email access works and save backup codes where a service offers them.
A PAC works whether the destination service uses a physical SIM or eSIM. Moving from physical SIM to eSIM with the same provider is usually a replacement or conversion rather than a PAC transfer: the provider moves the existing line to the digital profile.
A PAC lasts 30 days. If it expires, request another; the expiry of the code does not itself cancel the existing number. If a switch is delayed, contact the new provider with the PAC and submission details, ask whether it is pending or rejected, and keep screenshots or messages. Ofcom says providers may need to compensate customers for a delayed switch or loss of service beyond the allowed timeframe, but the amount depends on current rules and circumstances.
Ready to switch?
Text PAC to 65075 from the number you want to keep. Give the PAC to your new provider, which will arrange the number transfer.
PAC stands for Porting Authorisation Code. It authorises a new UK mobile provider to transfer an existing mobile number from the old provider.
A PAC is valid for 30 days. If it expires before use, request another.
STAC stands for Service Termination Authorisation Code. Use it when switching provider without transferring the existing number.
Text INFO to 85075 for contract-status and switching information without requesting a PAC or STAC.
Ofcom says a new provider must complete a standard mobile switch within one working day after receiving a valid PAC or STAC.
No. If keeping the number, do not manually cancel the old line first. Use PAC and let the switch close the old service.
Yes. A PAC can transfer a mobile number to a new provider whether the new service uses a physical SIM or eSIM.
Yes, but an early termination charge or other balance may apply. Check the switching information from the current provider before deciding.
When the PAC transfer completes, the old number should replace the temporary number on the new service.
The PAC, STAC, INFO and timeframe information on this page was checked against Ofcom’s consumer switching guidance, last updated 25 August 2026.
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