HUEY, I need you to update your "GamerTag" associated with your XG Profile and request a new username.
To update your "GamerTag" associated with your XG Profile, click "About Me" on your profile (directly above), click the yellow pencil next to "GamerTag", update it, then "Save".
To request a new username, click "Help Desk" on the top right corner of the screen, click "Request Login Name Change", type in your new GamerTag EXACTLY as it is spelled, then click "Request New Username".
Thanks,
FaceUp!