The SIM Swap can take anything from a few minutes to 24 hours to complete. However, the “norm” is around 30 minutes complete.
Please turn the device OFF/ON at 30-minute intervals until you get a signal and the SIM starts working.
If after the 24 hours your SIM swap hasn’t completed raise this with a giffgaff agent to investigate. To get in contact with a giffgaff agent please follow the link below to the agent form and fill in the text area or text box with the issue. https://giffgaff.com/support/questions