Did you request to have a number from another provider? if so, Your number transfer might still be in progress:
The transfer process:
At some point during the day, both SIMs will stop working (may be at different times) and after a while (this could be 10 minutes or several hours) your giffgaff SIM will start working again with the transferred number. You may find that calls, texts and data start working at different times and service may be erratic until the process is complete.
Have you tried turning your phone off/on again? If you haven't please do so periodically every 30 minutes.
If your number still hasn't transferred by 9am on the following day, you can raise a query to a Member Service Agent here https://support2.giffgaff.com/app/ask/Number-transfers/Transferring-my-number-to-giffgaff/form/
. Make sure to accurately complete the following information:
Existing giffgaff mobile number;
New mobile number (the one to transfer);
Alternative contact number;
Please do not contact the agents before 9 a.m. on the day following the transfer date as the process may be still ongoing and they could not act on it.