St Augustines case manager negligence

I was admitted into St Augustines hospital on the 26th February via casualty for headaches. I then did a brain ct scan in which it was found that I had severe sinus problems. I was then referred to an ent specialist at the hospital who had seen me on the 27th February. He had mentioned to me that I needed to do a sinus fess surgery . This was done on the 28 February. According to Umvuzo medical aid no authorisation had been sent through from the case manager for the operation to be done on the 28th February. However I was taken to theater and the operation was done. I have now been slapped with a huge medical bill by the ent specialist and the hospital as the medical aid is refusing to pay as they say that they did not get any updates of what needed to be done and they had only received an update on the 2nd March which they then responded to by saying that sinus surgery is an exclusion. However this was too late as the procedure was done on the 28th. So how can an operation be performed on a patient without first receiving authorisation from the medical aid and why was the medical aid not being updated by the hospital. Why was there an update only sent on the 2nd of March which is the day I got discharged. I am not willing to be held accountable for this bill due to the negligence of the medical staff involved in this process. I have never experienced any issues like this before as I have always known that authorisation needs to be granted before a procedure can go ahead. I need answers for this as it amounts to pure negligence so why should the patient now be accountable for what the staff was supposed to do. The lady at the ent rooms said that the case manager needed to get authorisation for the procedure and not them as I was admitted under another doctor's name. So is the case manager willing to be held accountable for this bill. Had I known that this was a scheme exclusion and had been informed by the relevant parties then I would of not went ahead with this procedure. I cannot understand how an operation can ne performed without getting authorization from the medical aid.