Please don't forget you must activate a sim that's not linked to your giffgaff account eg one from any members banner then follow this guide to move number back to giffgaff again
please follow this guide to Transfers hello an welcome my friend .
you will need to first make sure your phone is on 02 or unlocked
an that you have requested a pac code from previous network
if need a giffgaff sim card order one here please
an then activate your giffgaff sim with £10 voucher even an 02 voucher works.
before you can fill in the number transfer form with your PAC code . .
to activate your sim follow this link
http://giffgaff.com/activate an click on activate with top up voucher .
After your sim is fully activated this is when you can see your number here
and able to make and receive calls click on link below and enter your pac code http://giffgaff.com/support/transfer
the date format is like this eg 10/01/2019
also remember to input your old networks number without gaps eg 07 then the other 9 digits