I have already payed all my debt to the debt collection agency that I had owed back in XXXX because after I paid that amount I did not hear from the agency again. 
Now in XXXX, I get a letter from a different collection agency that I owe some other amount to the same creditor I had dealt with back then. 
I called the creditor and they had no information of mine besides what was noted from the previous debt collection agency. The previous debt collection agency did not document the full transaction. The creditor said that they changed debt collectors and the new one has gone far back as XXXX to collect debt. 
Unfortunately, I trashed all my documents that were dated back XXXX years ago and I 've also contacted my bank asking for statements from back then but they do not go as far back as XXXX years. 
I had high hopes in getting my bank statements because that would give me evidence that I paid more than what the creditor is asking. 
But I have no evidence of paying besides my memory and my letter to the debt collection agency I had saved in my email. 
What do I do? 
I have until this Friday for the debt collector to do something against me. I really do n't want to pay for something I already paid and am very upset about this whole mess. 
I do n't want to pay the creditor for something I already paid XXXX years ago and am just really upset this is happening. I 'm sure this is another way of scamming people of their hard earned money ... this is just unfair! 
Please help!! 

Thank you,