Just to be sure, I take it that you have gifted an email address to another person. That, in turn, has set up a separate BTID to manage that email.
Now you're looking to de-link it from that gifted BTID and put it back onto your main one to manage it?
If so, let me know as that's something that we can help you with.
Dunno if this is the right place to post it, but would like to say a big THANKS to the moderators who quickly sorted a problem with my BT Email account..