Bad service

On 23 September I visited the dentist for a root canal. Due to my medical aid being depleted the lady working with the accounts told me that I will have to pay cash directly after the consultation. The reception then told me the amount I owe (as showed on the system). I paid the full amount immediately after the consultation. A claim was still logged to my medical aid for a (cheaper) different amount. After a day or so I got an email saying I have an outstanding amount of R 97,40. The account lady reckons she doesn't work at reception, I must follow up with them why they let me pay a wrong amount. I did follow up, and the reception told me she just let the patients pay what the system says. And the amount that I paid is the amount the system showed. Nobody can explain to me why in the first place a different amount was claimed from my medical aid than what I paid, and secondly why is there an outstanding amount. My medical aid paid for the PPE that was used, which I also paid for? Then it was paid double?