This is a collection agency, that has many different numbers.  They will make it look like they are from your area, when in reality they are based somewhere else, such as Iowa or Minnesota.  As with any collection agency, ask for a copy of what they are talking about in WRITING.  If you don't remember a debt, most likely they are scam artists trying to get money from you.  Don't buckle.  They will tell you anything to intimidate you; it's their job.  Stick to the facts.  Anything they want needs to be in writing with actual dates, times, etc.  it's the law.

Bernadette has posted some excellent advice. A lot of times, though, you can't ask these people for anything because they hang up without leaving a name, a return phone call number etc. Keep in mind that  that is not your problem. If you do have the pleasure (or displeasure) of talking to anyone who works for businesses of this type, follow Bernadette's advice and DEMAND THAT EVERYTHING BE PUT IN WRITING. If you are fortunate enough to get a mailing address, send a CERTIFIED (RETURN RECEIPT REQUESTED) LETTER DEMANDING APPROPRIATE INFORMATION BE PUT IN WRITING.