Small claims...
....
It costs like $16 and is really easy. Just remember, you have to file in THEIR jurisdiction. You may want to call their local courthouse and have them fax or mail a small claims form. You may have to go there on the court date, but maybe they won't let it go to court. they'll probably call you with a better answer once they get their registered mail subopena.
Be prepared. Document everything..each call, names and dates etc. Also sue for about double the amount in punitive damages. It gets their attention, and if you do go to court, it will make it worth your while.
I hope it helps.