I've just done this, said a code would be with me within 7 working days. They said they've had to change the way the activation works because people have been setting up BT accounts to steal people's Gamepass? Can't imagine how that works to be honest.
They then told me I can get my phone cheaper so put me through to EE who transferred my mobile and broadband over and assured me I'll still get Gamepass.
Hopefully everything works out properly and I won't regret it. Bit more hassle than I expected when I got the text and email this morning.
