Contact the federal or state agency collecting the debt which is listed in the notice you received. If you need information about whom to contact, call the TOP Call Center toll-free at (800) 304-3107. If your debt has been paid in full, or if you do not owe the debt for other reasons, the agency collecting the debt is responsible for instructing Treasury to stop the offset process. They are also responsible for returning to you any part of your payment that should not have been reduced.