What you need to do:
Request your Porting Authorisation Code (PAC) from your previous mobile provider.
Just contact your current provider and ask them for it, saying you want to transfer your number to another network. They have to give you the number immediately, so the process won't take too long.
Once you have your PAC and an active giffgaff SIM, login and click herehttps://giffgaff.com/support/transfer
now to bring your old number to giffgaff.
Find out more about keeping your old number
Important note: On the day of transfer you will experience a loss of service during the transfer process. You may not be able to use either your old number or your giffgaff number for serveral hours up to 9pm on the day the number is transferring. Turn your phone on and off throughout the day.
What is the number transfer process?
Once you’ve completed the number transfer form, a few things will start to happen.
• Both SIMs will stop working, though not necessarily at the same time
• After a while (it could be 10 minutes or a few hours), your giffgaff SIM will spring back into action with your number now transferred
• Calls, texts and data will start working during the day, though not all at the same time.