A letter of reply / response regarding a purported error stated in a collection letter. It confirms and reiterates the correct outstanding amount as per the system, and request the client to check his record again and discuss further for any discrepancies.
Thank you for writing to us about the “error” in our collection letter. We can understand why you are upset if it is a genuine “error”. However, we have checked our records and according to our system, you still owe us [amount].