Ok so last night somehow my gamertag got deleted

and now I cant play FFXI.
So I need people to answer 2 or 1 question either one you can answer
My Questions....
1) How can I get my gamertag back so I can play FFXI again?
2) How can I change the gamertag of the Play Online account so I dont have to use the gamertag its setup with right now?
Thanks to anyone that can help me,
-Icey