I was made to pay an account already paid by medical aid!!

I had a diagnostic procedure done in January 2024. Lake Smit & Partners demanded an immediate payment and I explained the claim was being assessed by my medical aid and would be paid within 30 days. After the 30 days they still demanded payment saying medical aid had only paid a portion of it and I had to pay the balance. They were dishonest in that they only showed me one of two payments they received and they were threatening to handover the account if I did not pay. I made my payment on 26th Feb and now I have proof that medical aid had paid that account on 1st February, which was within the 30 days. Can Lake Smit & Partners explain why they were not honest about both payments made on 1st February? They are very quick to threaten handing over the account. When are they paying back my money that they have been keeping for 3 months now?