claims not paid in full,after authorisation.

I was involved in an accident around February last year, which cost so much scars and skin problems on my face, to cut the story short my surgeon wrote a motivational letter regarding the drafting of my face skin and so fourth which eventually bonitas authorized for surgery which i did in august 2018.My problem is that thou they authorized they did not pay the full amount of the surgeon, at least not even half of her bill thou they authorized the procedure. now they have cost me unexpected debts with the doctor which i don't have the money to pay her and they are even taking me to credit bureaus thru their lawyers.I think its unfair of Bonitas being with them for over 5 years and most years would even pass without me even claiming on my medical aid as i am not a sickly person and the 1 time i need them the most they decided not to pay the bill.i feel this is very unfair i need them to explain to me the reason they cant pay the doctor as this is making me consider changing the medical aid with them.