Medical aid approving things and not paying for it afterwards

My wife needed to go for an operation to remove wisdom teeth. So the doctor sent a letter to Medshield to approve the surgery, we then got an approval letter from Dennis, their dentistry division saying its approved and they will use the specialized dentistry funds for the surgery. She had to go in for an Operation as she has a heart condition and needs to be sedated, the dentist cant do it without her sleeping hence needing it to be in hospital and sleeping. The doctor then did the operation and Medshield didnt pay for a specific code as its apparently not covered by my plan but the circumstances are not normal hence we asked for approval and got it. If we didnt get the approval we wouldn't have done the surgery. Now I need to fork out thousands which is not fair as we got an approval from Dennis!