Poor management

I had a sinus operation last year September and medical aid authorized and approved for my operation. Months later I was shocked to receive a statement that I owe almost R40 000 for a sinus operation. I have done this operation many times and always medical aid paid. Now medical aid says I owe them money for an instrument that my Dr used during the operation. So I must pay for instruments used during the operation? Medical requested that my Dr writes them a motivation explaining to them why he used the instrument and also asked for Dr's codes. My Dr emailed them all the medical aid requested but until today, they have not paid the claim. Everytime I speak to an agent at the call center they fail to assist and they refer me from one agent to another without a solution.