Third-Party Debt Collectors Must Abide by the Fair Debt Collection Practices Act (FDCPA), 15 U.S.C. Sections 1692-1692p, which sets forth protocol for making third-party debt collection calls. 

For example, under 15 U.S.C. 1692c, third-party debt collectors may only contact consumers after 8:00 a.m. and before 9:00 p.m.

Generally, under 15 U.S.C. 1692c, third-party debt collectors may not continue to contact consumers who have notified the collector, in writing, to cease all further communications.

For more information, contact:  the Federal Trade Commission at ftc.gov or 1-877-FTC-HELP (the FTC publishes a great FDCPA handbook for consumers).