Appalling service from massmart gap cover

I had a procedure done in hospital on the 26th August 2020. I had authorization to go ahead. There was a shortfall for the doctor and anesthetist which would be covered from gap cover. It is going on 6 months and massmart gap cover hasn't paid the outstanding amounts that are due. Each time I call them to find out what's happening they have a different story or excuse. The doctors want to hand me over as this account is long overdue. I'm getting very frustrated as I have been paying for massmart gap cover for many years. They promise to call back and resolve the matter but still no joy.