The Fair Debt Collection Practices Act (FDCPA) provides you recourse. It may entitle you to money damages and you can do this for free as legal services are covered by the debt collector.
What you describe could be a violation of the Fair Debt Collection Practices Act (FDCPA). Violations of the FDCPA entitled you to: 1. money damages, 2. free legal help and 3. Have the calls stop for good!
