Did you report to SSA that your rep billed you $500 for winning your case? While fees for medical records/copying etc are allowed, reps are not allowed to just bill because there is no backpay. He could lose his ability to represent claimants to SSA.
The rep's letter did say the explanation was for requesting medical records and postage. In my letter to SSA removing him as our representative, I wrote that we paid him $500 for 2 hours of work, noted he did not request any medical records, and that he had about $10 in certified mailing fees. We wrote in that letter to SSA that he asked for that amount since he didn'r get any backpay. We added that we paid it to him because we appreciated his support and the rapid approval, but that reiterated the fact that his service to us was concluded, and he was no longer represented by us.