Product: Debt collection

I was contacted by Pioneer Credit Recovery by mail in a letter dated XX/XX/XXXX. In the letter, it was stated that I owe money to the Department of Defense for XXXX overpayment to XXXX XXXX for prescriptions dispensed to me between XXXX. The overpayment amount was {$3300.00}. That debt is legitimate and I own it and am glad to pay it. However, the total amount that Pioneer is trying to recover from me is over {$6100.00} due to administrative costs, penalties, and interest. 
I was shocked, as this was the first time I was hearing about any monies owed to XXXX, from nearly 7 years ago, no less. Apparently, XXXX XXXX  was sending correspondence regarding the overpayment to an address I was no longer living at, despite having my mail forwarded from the previous address to the new one via USPS. I have my ledger from my previous apartment that we were renting at the time showing when we made our last payment and the real estate contract showing when we purchased and moved into our new home. This happened nearly 11 months before they started sending letters about the overpayments. I can only assume that if the new residents received these letters meant for me, they tossed them rather than returning them to the sender. XXXX XXXX  states they never had any returned correspondence, therefore assuming I got the letters and was ignoring them. 
This information is beside the point, but my credit score has been over XXXX points for years. I have integrity and pay debts I owe ( obviously when it is a debt known to me ). I am in no way trying to avoid paying XXXX XXXX. The excessive fees and costs added on to the original debt, however, are unfair. I reached out to XXXX XXXX, who states they no longer own the debt and couldnt help. I then contacted XXXX XXXX to inquire about the debt and they couldnt find any record of it anywhere. I have spoken to XXXX from Pioneer Credit Recovery several times trying to explain the situation and have not gotten any alternative recommendations on how to appeal the tacked-on fees. She simply added that I can either take out a personal loan to pay the balance or my wages could begin being garnished or a lien could be placed on my home, which were all scary thoughts and made me very anxious. I sent a dispute letter on XX/XX/XXXX, which was forwarded to the XXXX XXXX XXXX XXXX. They responded on XX/XX/XXXX by mail stating that the original debt owed to the Department of Defense was valid and to proceed with collection efforts. Again, I am happy to pay a debt I owe as long as I know I owe it.

I was unable to find any direct phone number to the XXXX XXXX Dispute Resolution division at the Treasury Bureau of the Fiscal Service. They only have a fax number and email address listed to the public for use if the consumer has any questions regarding the dispute. I sent an email to them on XX/XX/XXXX to further discuss everything previously laid out in this letter, and got an automated reply that I could expect a response to my inquiry within the next 60 days, which is not very helpful in reaching a prompt resolution while this debt continues to accrue interest. I also sent a letter by mail on XX/XX/XXXX to XXXX XXXX XXXXXXXX XXXX with an address provided by a XXXX representative during one of the handful of phone calls I made to them trying to get answers. As of today, Ive yet to get a response by telephone, ground mail or email from them. 
With fees and penalties accruing for 5 years before I was ever notified and made aware of the debt, I dont know who to appeal to at this point to discuss forgiveness of these extra charges. I would love to pay off the original amount I owe, make the situation right, and close the book on this, but Im feeling indignant as a responsible consumer. Every avenue I have gone down to try to amend this situation on my own has lead me to a dead end and Im running out of ideas on where to turn next. This is simply unjust practice by Pioneer Credit Recovery and I am hoping they can see that each individual has a different story, that some of us are responsible and honest and simply looking for resolution, and that wrongs can be righted in a situation such as this. 

I have enclosed all documentation and correspondence between Pioneer and myself since XX/XX/XXXX, along with my documentation proving I was no longer at the address on file with XXXX XXXX when they began sending me notices about the debt back in XXXX, and my letter to the XXXX. Hopefully you are able to help me make some headway with Pioneer Credit Recovery or XXXX XXXX XXXXXXXX XXXX to settle this debt fairly.