If you think your bank is doing something so bad that it violates banking regulations, here are the groups that officially regulate banks. Complaining to them might not help your individual issue, but enough complaints could bring some attention on the banks that they would prefer to avoid:
The Federal Reserve
Board of Governors of the Federal Reserve System
Division of Consumer and Community Affairs
20th and C Streets, NW, Stop 801
Washington, DC 20551
Office of the Comptroller of the Currency
Use FDIC’s Bank Find to find specific agencies for your bank.
Write a formal complaint letter to the bank’s regulatory agency. Follow the FTC’s instructions for writing a complaint. This document also has the correct contact information for the various regulatory agencies.
State Attorney General
Google for your local state attorney general’s office