Having to pay again, why am I paying you Discovery

Please Discovery explain to me why I am paying you THOUSANDS every month and then when its your turn to look after me I end up receiving the bill. When I was hospitalized in November we got authorization from you for the necessary hospital stay. I dont understand why I am being held liable for money to a hospital when I have full hospital cover? I've just reached the end of the line with fighting about everything. While I was in hospital I asked my doctor (Discovery Network GP) if the hospital stay would be covered by the medical aid and was assured that everything would be sorted out and I need not worry. Well what a surprise when the hospital informed me that I owe them nearly R4000.00 that Discovery is not going to cover as there was only authorization for a certain amount of time. Does Discovery arrange with the doctors on the network list that the patients are misinformed so that we end up being responsible for the accounts?