stolen username

You would need to contact support and have them start an unauthorised access investigation.

http://support.xbox.com/contact-us

to below

nope, only by contacting them via chat or phone and opening an unauthorised access case.

ahhh ok ill try get in contact with them

when i try to do a live chat with them it just puts me on a white screen is there any other way of me getting my username back?

you will need to contact microsoft over a compromised account

compromised account

they can then look to see what has gone on, they will lock the account while they investigate as they will have a log of who used the account and where and who may of changed it via ip and other means.

Support would be the only ones who could do anything if possible. Otherwise, you'd have to just change your gamertag, but since it's already on another account, that wouldn't be possible.

@(Farscape) - That phone number is no longer a direct line to support. It just sends you to the contact website.