Bill collector/they will not stop till they have what they want or untill statue of limitations runs out, which is usually 4 years or 6 years,from the last payment made. or you could always ask for there address and send them a letter to validate the debt , would you pay anybody that says you owe them money, who is to say how much u really owe?..let them know that you need to see a break down, of what is owed, how would they arrive at a number like 456.33? someone had to of calculated that? third party collection agency do not have the right to collect anything, they buy these bad debts in hopes of getting anything..thats why they are willing to settle for 50-60-70 %off, they buy them for penny's on the dollar..