Incorrect Pre Auth & incorrect billing

Turnaround time around claims or queries has to be the worst when it comes to this medical aid . I was admitted at Sunninghill hospital & my pre auth was approved. When my medical bill came it stated that I was admitted under PMB , which means Prescribed Minimum Benefits by medical aid. I have been requesting them to relook at my Pre auth for a review or liaise with the hospital with regards to this , as my GAP wont reimburse me due to the fact that this a PMB case. I have outstanding medical bills due to this incorrect auth or billing & i am stuck its been weeks of back & fourth . Spending my time & money trying to get someone to resolve this ... Its really disappointing. My next step will have to be the ombudsman .