Unauthorized Character Transfers

So, the story goes I quit wow about a year and a half ago and I decide a couple days ago I wanna play again. Well I try to get my account all set-up and I find out someone has been playing on my account for the last 6 months! Needless to say I was shocked, anyways I was able to recover my account no problem there.

Now the problem comes from whoever was using my account transfered all of my highest toons to one server and I want them back to there original servers so I can play this game with my friends again....like intended!
So, what steps do I take to get these characters back to there proper places? Any help would be GREATLY appreciated!