If a collector violates the FDCPA, you have real recourse:
File a CFPB complaint. Go to consumerfinance.gov and file a complaint. The CFPB forwards it to the collector, who must respond within 15 days. Companies take CFPB complaints seriously because they trigger regulatory attention.
File with your state attorney general. Many states have additional consumer protection laws that go beyond the FDCPA. Your state AG can investigate and take enforcement action.
File with the FTC. The Federal Trade Commission maintains a database of consumer complaints and uses it to identify companies for investigation.
Sue under the FDCPA. You can sue a debt collector in federal or state court within one year of the violation. You can recover: actual damages (stress, lost wages, medical bills from anxiety), statutory damages up to $1,000 per lawsuit, and attorney's fees. Many consumer rights attorneys take FDCPA cases on contingency (they get paid from the settlement, not from you).
Class action potential. If a collector is using systematic illegal practices, a class action suit can result in statutory damages of up to $500,000 or 1% of the collector's net worth, whichever is less.
Document everything. Keep a log of every call (date, time, what was said), save every letter, and if legal in your state, record calls. This documentation is essential if you pursue legal action.