1) Find and buy a new phone or SIM deal from Three
Out of contract and ready to switch? Good news. Your next task is to sign up for a new phone contract or SIM only deal from Three. Once you’ve passed Three’s credit checks, you’ll receive your phone in the post.
2) Contact Three to give them your PAC code
We’re almost there now. Next you’ll just to ring Three to give them your PAC. You can reach their customer support team on 0333 338 1001 from a landline (standard network rates apply).
3) Insert your new Three SIM card
If you got a new phone as part of your contract, take the pin-key included in the box and unlock the handset's SIM tray. Then insert your Three SIM card.
If you went for a SIM-only deal instead, you can just put the Three SIM in your existing phone.
While the number transfer is taking place, you’ll be given a temporary phone number that you can use and on which people can contact you.
4) Wait for your number to be transferred
The transfer should be complete the next working day. However, this can vary from network to network and sometimes depends on whether the day after you make your call is a working day or a weekend.