Product: Debt collection

I had multiple doctor bills and I was behind on paying them all. I was systematically paying them off as I began to understand my medical costs. I paid XXXX checks to my doctor 's office ; 1 cleared on XXXX/XXXX/XXXX for {$110.00} and the other on XXXX/XXXX/XXXX for {$270.00}. I mailed both checks to the doctor 's office directly as I was unaware that a collection agency was notified. The collection agency is requesting payment of app. {$120.00} now and will not breakdown in detail what makes up the {$120.00}. I did not pay the collection agency and they did nothing to collect the debt, but I can only assume they are requesting their fee. My doctor contract does not state a % for interest fee by a collection agency. I have asked the collection agency twice by sending back their payment stub to stop contacting me, I paid the doctor in full and to give me a breakdown of the cost. I have recently sent a letter to them stating I do not owe this debt and the balance with the doctor is XXXX. The collection agency has failed to provide me information on this debt, continues to possibly affect my credit for a debt that does n't exist other than a fee which I refuse to pay to them. I calculated the fee to be app. XXXX % of my total cost if that is truly what the debt is for. They did not provide account number on the latest collection notice. The second notice I got said they may possible sue me for the debt. I did not recognize the bill at first due to the number of medical bills my family had so I assumed it was valid at first and part of the money I already paid my doctor 's office. After reviewing my medical records with my insurance company I noticed the {$120.00} did n't match anything, so I am disputing it. Again the doctor 's office is confirmed paid in full. I am wondering the interest rate they can charge? How I can get a breakout of the cost and can they continue to put their fee as uncollected medical debt on my credit report even though they were n't paid anything? I feel the fee should come from the doctor 's office if they need to get paid if they are to keep some of the portion of the bill that was paid not me. I am having a hard time figuring out if their interest rate percentage is legal? Can they continue to request payment on a debt that is paid in full to the doctor 's office? Why they are refusing to breakout the {$120.00} so I can see what makes up the bill? And if they can put their " collection fee '' on my credit report as unpaid debt thus effecting my credit score? I have seen no proof that they provided any level of service to collect the doctor 's debt. The checks were directly payable to the doctor 's and if they feel they are owed money then they should go back to the doctor 's office and collect their fee. I 'm not really asking to file a complaint unless it is warranted. I would rather see the {$120.00} get removed from my credit report if it 's there and they stop sending me letters after I told them to stop or provide backup to the debt. I would like to state that I signed the doctor 's payment letter under duress as I was XXXX sick, lost XXXX pounds in a month and could n't eat. I wound up having an XXXX that was painful and signed the papers because i did n't have an alternative. I know that does n't really mean anything but I was n't worried about what the contract stated as I was only concerned with getting better and being able to eat again. After my insurance adjusted the many medical bills I had, I paid all the debts I could as fast as I could even getting gift money to do so. I have over paid numerous medical bills in the process only to receive checks back. All costs were created XX/XX/XXXX but I am not sure when my insurance company finally adjusted, approved and paid their portions as it does n't tell me that without looking on previous statements. Many times my insurance company sent revised billing statemnt