From Consumer Wiki
Tour agencies sell packaged tours to travel agencies, buying in "bulk" from suppliers such as airlines, hotels, bus companies, cruise companies, and other tour operators. Tour agencies may have their own associations to mediate disputes.
The National Tour Association will take complaints about a tour agency (if a member of the association) and mediate between parties; otherwise, it becomes a Better Business Bureau or civil issue.
National Tour Association
United States Tour Operators Association