I got that error code (80154002) when i attempted to change my GT to another Microsoft ID. When I signed in (with the same microsoft ID) at xbox.com my gamertag was CatchyBasher95 (the website created that tag for me) but on my xbox my GT is "Sinkaa91". I always get e-mails about the Live Gold subscribing. I've refreshed my security proofs via live.com and xbox.com and changed the password too, and after this I can signing in Xbox and the website, but nothing has changed. I dont have any ideas how to continue. i've phoned the hungarian support, but they've told me the same i can find at http://support.xbox.com/hu-HU/billing-and-subscriptions/account-management/manage-microsoft-account#9612b19bb2684f1a9ebf5affb8dd256b.
(sorry for my english, if i took any mistake)