Careful with that covert ad .... Repeat calls are too simple to defeat to go retaining a lawyer. It takes a brief letter requesting validation or a cease-comm. The FTC and many consumer groups describe how to draft and submit. Of course, should one's demands be ignored or rights be violated, then legal aid is a fine option.
If you are receiving repeated, misdirected, and/or abusive calls from a third party debt collector, you may find relief in the provisions of the FDCPA, the Federal law which regulates collector behavior. Learn your rights at FTC-dot-gov. See also your state laws for additional support.