500 FastCash not sure if being ripped off Web Only Internet

I'm not sure if I'm being ripped off or not... This company, 500 fast cash, has called me intermitently in the past year or so. They would call me for what it seems like every 3-4 months, telling me that I still owe them 510 dollars. I paid off this account though I nolonger have the documentation, but I took out a loan through my bank to may them off. In the most recent phone call they threatened to forward my account to a 3rd party collector so I told them that I dont have that kind of money. I told them to please send me a letter stating my account number, and the amount I owed to which the person on the other line stated they cant do that. I'm not accusing them of anything but it seems very odd to me that this company could not send me a letter stating anything. It is also very odd to me that they would not follow up on the account aggressively as other loan institutes would. I have dealt with other fast cash people before and from experience all of them are pretty persistent about collecting an existing debt, this company is the only company I know that would only call sporaticall (every 3-4 months) to remind me of the debt as opposed to every week, or in some cases, everyday like the other companies. I asked them why so sporatic with the phone calls and the man simply stated that my account wasn't up for review...If my account is in default status, I would assume that my account would have been reviewed a number of times and that I would have received a thousand phone calls to notify me of the status, or even a letter, the guy even stated that the last time they spoke to me was in November of 2005, it is now August of 2006, Its hard to believe that it would take them 8 months to realize that I still owed them money. Am I being scammed, or is this a customary thing for the fast cash companies to do? My gut instinct tells me that there is something fishy going on with this situation, with them not being able to send me a letter of any sort and with the calling patterns. If anyone has any suggestions I would greatly and truly appreciate it.

Travis
Annapolis, Maryland
U.S.A.