oxford settlement receipt

Hello Nelly; I settled with oxford in '09 and now someone else is calling for the same debt. I request a receipt be sent to me 3 times and to this day have not received it. The someone else that is calling now about the same debt is saying that there is a government judgement against me now because I still owe all this money and when I advised her that I settled she said that if I don't have a piece of paper to back up that claim then I would have to pay again. How much of that is true and how may I proceed from here. To begin with I'm not employed therefore it is impossible to pay a debt that I no longer owe, second, I already owe taxes from a couple of years ago so it seems to me that the 'snowball' is gathering more and more. HELP!!