Criminals masquerading as debt collectors attempt to extort money from people by scaring you into believing that you will be criminally charged (they use the bad check or hot check claim a lot) and go to jail, lose your driver’s license, have wages garnished without actually being sued or going to court, be sued, and a variety of other variations on this, all for an alleged or nonexistent debt. One of the tricks they use is to call your family, friends, neighbors and/or places of employment (past or present or both) to create panic and embarrassment so that their intended victim calls them and they can scare that person into paying their extortion money. They also use the “process server” ruse who calls and claims he is going to serve you, but then says you could avoid it by calling another number where they will ask for money to “make it go away” (this is actually the same place, they work in teams, one pretending to be the server, and the other usually pretends to be a lawyer). Process servers do not ever call ahead so that you can dodge them. Process servers get paid to serve papers, nothing else.
Read up on your rights here and also make a complaint at this government site: http://www.consumerfinance.gov/
Also file a complaint with your State Attorney General's office.
List of State AG’s offices: http://800notes.com/faq/attorney-general