Unpaid bils

I have undergone a medical procedure last month. Upon obtaining my authorisation code I was told that the doctor performing the operation was not registered and that there might be additional charges from the doctor that might not be covered and I understood that and agreed to it. Upon receiving the bills from the doctor and hospital only half of both invoices will be paid by Bonitas. There was no agreement on any costs that will be paid by me to the hospital costs. Why was the hospital account not paid in full? Why do I have a medical aid if I need to pay half of the medical expenses? Previous doctor connotations at specialist for myself and son, I have claimed from Bonitas and to date have had no response or payment.