Once you have decided to join O2, you will need to contact your existing network provider to request a PAC number (Port Authorisation Code).

Then, once you have received your new O2 SIM card, you will need to give O2 customer services your PAC code. The easiest way to do this is by completing the form at o2.co.uk/keepyournumber. Once we have received your PAC code, your existing number will be transferred to your new O2 account within two working days.

Remember your PAC code is only valid for 30 days.

If your number is currently on O2 Pay & Go, no PAC code is required to transfer your existing number across to your new SIM card. Just call customer care once your new contract sim has arrived on 08705 678678. Your number will be transferred within two working days and any existing balance will be transferred and appear as credit by your second invoice.