Hi, are you trying to log in with your number?
Once you bar your sim, you can't then log in with your number, you must use your username
Do you receive emails from giffgaff When purchasing a goodybag or topping up?
And can you still access that email account?
Go to the email received from giffgaff around the date you last topped up or purchased a goodybag
tour correct username will be mentioned in the top right corner of that email