do you mean you used the get a new number option here
Rather than transfer a number to giffgaff?
And you can't log into the account linked to your number?
Did you log in with your number rather than your username?
Could you say what your username is or aren't you sure of that?
Is your phone showing signal bars and a connection symbol
(3G, 4G, H, E, gprs)
From your phone keypad dial
Star 100 star 7 hash
And press call
Do the same with *100#
What word or words do you see on the phone screen?