How to Switch SIM and Keep Your Number

Since Ofcom's "text-to-switch" rules came in, switching UK mobile networks takes one text message. You keep your number, your old contract ends automatically, and the whole process is free.

This guide covers the exact steps, what to do before you switch, and the common problems people hit. If you haven't picked a new network yet, compare options on our SIM only deals page first — both Giffgaff and Lebara post SIMs out free.

What is a PAC code?

PAC stands for Porting Authorisation Code. It's a unique code that tells networks to move your existing number to a new provider. Under Ofcom rules, your current network must send it to you immediately when you text PAC to 65075 — and they can't charge you for it or try to keep you with retention hold music.

The text-to-switch process also automatically tells your old network that you're leaving. On a rolling monthly contract, your billing ends when the number transfers — no notice period, no exit fee.

Step-by-step: switching SIM and keeping your number

• Step 1 — Pick your new network. Compare plans first: our SIM only deals and Giffgaff vs Lebara pages are good starting points. Order a free SIM — it arrives in 3-5 working days.
• Step 2 — Check your contract status. On a rolling 30-day plan you can leave any time. On a fixed-term contract, leaving early may trigger remaining charges — the PAC request won't tell you this, so check first.
• Step 3 — Text PAC to 65075. From the phone whose number you want to keep. You'll receive your PAC code and account info by text within minutes.
• Step 4 — Activate your new SIM. Insert it and follow the network's activation process (online for Giffgaff and Lebara). Choose your plan — you can change it every month later.
• Step 5 — Give the PAC code to your new network. Usually in the activation flow or account dashboard. The transfer completes in 1-2 working days, typically with a brief loss of service at the switch moment.
• Step 6 — Test and tidy up. Make a call, send a text and check mobile data. Your old SIM will stop working once the transfer completes — recycle it.

Before you switch: 4 things to check

• Outstanding credit or device payments — settle any balance on your old account to avoid surprises.
• Voicemail and backups — save any voicemails you want to keep; they don't transfer.
• Accounts linked to your number — banking 2FA, WhatsApp and delivery apps keep working (your number moves with you), but double-check any service that texts a code to the old SIM during the switch window.
• Coverage at your address — use the new network's coverage checker. O2 (Giffgaff) and Vodafone (Lebara) both publish postcode-level maps.

Common switching problems (and fixes)

• "My PAC code expired." PAC codes last 30 days. Text PAC to 65075 again for a fresh one.
• "I lost service before my new SIM worked." There's usually a short gap on transfer day. Insert the new SIM and restart the phone; it connects within a couple of hours.
• "I want a new number instead." Skip the PAC code entirely — just activate the new SIM and it gets its own number. Cancel the old SIM separately.
• "I'm on PAYG with credit." Unused credit doesn't transfer, but you can request a refund from your old network after switching.

Does switching cost anything?

No. The PAC code is free, text-to-switch is free, and rolling monthly networks like Giffgaff and Lebara have no exit fees. Your only cost is the new plan itself — from around £5/month. If you're mid-contract with a fixed term, check whether remaining charges apply before you request the PAC.

Final thoughts

There's no longer any practical reason to stay on a bad mobile deal. Text PAC to 65075, order a free SIM from a better-value network, and your number follows you within two working days. Because rolling plans have no contract, you can keep re-checking the market every few months — switching is always free.