Porting Your Mobile Phone Number In The UK
Summary and Conclusions
Porting your mobile phone number between two networks in Britain is easy. Just call your current network and ask for a Porting Authorisation Code (PAC). If you're signing up for a contract with a new network, give them the PAC when you sign up, otherwise call them and give them the PAC when your new contract or Pay As You Go service is up and running.
The PAC has to be used within 30 days, and once you have given your PAC to the new network, your number will usually be ported in one week, although it may take up to a fortnight. The network you are switching to will give you the date on which the transfer will take place, and until then your number will still be usable on your old network.
Being able to keep your mobile phone number when you move to a different mobile network is fantastic because you can save money by switching, without the disruption of telling everyone a new number. Do remember to tell people your new network so they can tell if calling you on their mobile will be a cheap same-network call or not.
So if you are thinking of switching to another network, don't be scared of porting your number!