Despite asking several times, you are yet to confirm that the correct mobile number is shown on that account.
When is the last time you used this SIM card?
Please confirm that the correct mobile number is shown on your account: https://giffgaff.com/dashboard
What do you hear exactly if you dial your number from another phone?
I thought you're not supposed to share personal info, e.g. your mobile number?
I'm not asking you to share the number, just to check that the number you see is the one you expect to see.
Call the number shown on your account from another phone - does your phone ring?