Incorrect Billing

My son was admitted in hospital at Netcare Alberton Hospital, and was in hospital for 3 days, after we got discharged I got the claims statement from Medical Aid and as per the statement, all of the claims submitted by the hospital and the doctor were paid and paid in full. To my surprise I received a statement from Netcare that I owe the hospital R2428,05. I then took upon myself to call Netcare so I could get some clarity on this and Lesedi the gentleman I spoke to couldn't tell me where that balance was derived from and he mentioned that there is a 30min rule that needed to apply which was not app**** and also mentioned that I SHOULD call back next week Monday to get an update on this. Let's get 1 thing straight, I will NOT call back Netcare to get feedback on an error from them, I called them to make them aware of the error, it is their responsibility to make sure they rectify their mistake and call me back with feedback and confirmation that the issue is sorted and I do NOT owe them anything. Also I am not willing to wait until next week to get feedback, there is no way it will take Netcare 7 days to rectify this and clear my account, can I get some level of commitment on when I will get feedback, not next week, this week PLEASE!!!! Even the service at the hospital leaves little to be admired just to put it out there.