DO NOT pay these people a single penny!!!
DO NOT answer their calls or reply to their mail!!!
3 years ago I moved out of my apartment and was sent a refund check from my deposit. I did not owe them anything, in fact they paid me back. A few weeks ago I get a piece of mail from National Credit Systems saying that I owed the apartment complex money and that they were collecting. I knew for a fact this wasn't true as I checked back with my old apartment complex and they had no record of a debt, just my positive balance that they had already paid me for.
I started doing some digging and found that pretty much everyone who has dealt with this company either didn't actually have any debt or had already paid their debt. Apparently their tactic is to get old records and then send out fake bills. If they get a "bite" aka you answer their calls or reply to them in any way, they tag you in their systems to keep contacting you, because they know at this point you think the debt may be real.
I hope this helps anyone one who is looking this company up to find answers. The best thing to do if they try and contact you, is to report them to the Consumer Financial Protection Bureau at the following link:
The company needs to be shut down