You can complain to the Office of Consumer Affairs under your state's Attorney General. You can also file a complaint with the FCC, which has a special web page explaining the process. Google: FCC Cable Television Fact Sheet
You are better off trying to negogiate with the cable company. No reputable company would knowingly overcharge their customers. Take your solid evidence and speak to a manager.
You first have to go through the process with the company and document it carefully. Then find who regulates utilities in your state and file with them- your Secretary of State Office can help, or consult your State's Attorney General Office.