You have the legal right to keep your mobile number when switching to any UK network. The process uses a PAC (Porting Authorisation Code) and is straightforward — here is exactly how it works.
The Three-Code System
| Code | Name | Use case |
|---|---|---|
| PAC | Porting Authorisation Code | Keep your number when switching (most common) |
| STAC | Service Termination Authorisation Code | End contract without keeping number |
| Request a PAC via text: “PAC” to 65075 | Free, immediate | Standard route |
Step-by-Step: Keeping Your Number
Step 1 — Get your PAC
Text PAC to 65075 (free from any network). You’ll receive a text response with your PAC code within seconds or minutes. Your network must provide it within 1 working day under Ofcom rules.
Alternatively, call your network’s customer service and ask for your PAC code. They cannot refuse or make you jump through unnecessary hoops.
Your PAC will look like: Three letters, then a dash, then six digits. E.g. ABC-123456. It is valid for 30 days.
Step 2 — Sign up with your new network
Choose your new SIM-only deal and sign up. You will be asked for your PAC code and your current phone number during the sign-up process. Provide both.
Step 3 — Wait for the switch
Your number will be ported on the date your new provider specifies — usually 1 working day after you provide the PAC. You may see a brief 30–60 minute outage during the transfer.
When the switch completes, your old SIM will stop working and your new SIM will be active with your existing number.
Step 4 — Check your old contract
Your old contract ends automatically when the port completes — you do not need to separately cancel. Any early termination fees still apply if you switch before the end of your minimum term.
What Happens if Something Goes Wrong?
If your number fails to port correctly, contact your new network first. If unresolved, contact your old network. Ofcom requires both to cooperate promptly. If neither resolves it, complain to the Communications Ombudsman (free and impartial).
Unlocking Your Phone
If your phone is locked to your current network (common with contract phones), you need to unlock it before the new SIM will work. Under Ofcom rules, your network must unlock your phone for free on request. This can take up to 10 working days.
Contact your network’s customer service and ask specifically for an “unlock” or “SIM unlock” — provide your phone’s IMEI number (dial *#06# on any phone to find it).
For choosing a SIM-only deal to switch to, see Best SIM-Only Deals UK 2026.
Can You Keep Your Number When Switching Networks?
Yes — switching mobile networks does not mean losing your number. This is guaranteed under Ofcom rules. The process uses a PAC (Porting Authorisation Code) — a code from your current network that your new network uses to transfer the number.
Timeline: Number porting typically completes within 1 working day after your new SIM is active. Some ports complete within hours; others take until the next working day.
International calls concern: If you are on a contract with international calls included and your new network does not include them, clarify before switching — this is one area where not all plans are equivalent.
Network Coverage — Check Before Switching
Coverage varies significantly between networks, particularly in rural areas:
| Network | Coverage (UK outdoor, approximate) | Best for |
|---|---|---|
| EE | ~99% population | Rural and remote areas |
| O2 | ~99% population | Strong urban and suburban |
| Vodafone | ~99% population | Urban and major roads |
| Three | ~97% population | Good urban; can be weak rural |
| giffgaff (uses O2) | O2 network | Budget; O2 coverage |
| Smarty (uses Three) | Three network | Budget; acceptable urban |
Use the Ofcom coverage checker (checker.ofcom.org.uk) to compare actual coverage at your home and workplace before switching.
Can You Keep Your Number When Switching Networks?
Yes — switching mobile networks does not mean losing your number. This is guaranteed under Ofcom rules. The process uses a PAC (Porting Authorisation Code) — a code from your current network that your new network uses to transfer the number.
Timeline: Number porting typically completes within 1 working day after your new SIM is active. Some ports complete within hours; others take until the next working day.
International calls concern: If you are on a contract with international calls included and your new network does not include them, clarify before switching — this is one area where not all plans are equivalent.
Network Coverage — Check Before Switching
Coverage varies significantly between networks, particularly in rural areas:
| Network | Coverage (UK outdoor, approximate) | Best for |
|---|---|---|
| EE | ~99% population | Rural and remote areas |
| O2 | ~99% population | Strong urban and suburban |
| Vodafone | ~99% population | Urban and major roads |
| Three | ~97% population | Good urban; can be weak rural |
| giffgaff (uses O2) | O2 network | Budget; O2 coverage |
| Smarty (uses Three) | Three network | Budget; acceptable urban |
Use the Ofcom coverage checker (checker.ofcom.org.uk) to compare actual coverage at your home and workplace before switching.