They are scammers. They tried this garbage with me and I happen to know the law. First of all its against the law for them to threaten criminal action under the Fair Debt Collection Practices Act. Second of all, they allege that I took out a payday loan, and then said something about a bad check. If they were legit, they would know there's a statute of limitations for prosecution in most states of 2-3 years.
They were all over the map. I had them chasing their tail trying to answer my questions and come clean, so they hung up on me, and now won't answer the phone when I call.
This is a common ploy by criminals masquerading as debt collectors who are attempting to extort money from people by scaring you into believing that you will be criminally charged, go to jail, lose your driver’s license, have wages garnished, 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 work place, friends, or relatives repeatedly in an attempt to shame you into paying. 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. Please note that process servers do not ever call ahead. That way you can’t dodge them.
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
Get a call blocker. I would also ask for documentation regarding the alleged debt. I would then send them a certified letter telling them to stop calling you. Be sure to keep a copy for your records.