Lack of payment for MRI

I have submitted various emails to Discovery regarding payment for my wife's MRI. this was needed to enable the surgeon to decide the procedure for a sever back pain, which resulted in an operation. It was the opinion of the doctor and the MRI people that the majority would be paid should an approved operation take place, which it did. Even though my medical aid is hospital only. The reason they believed it would be paid (or part paid) as previously doctors booked people into hospital just to cover payments for MRI. Discovery have stated that the relevant codes do not indicate a PMB diagnosis BUT do not say which codes would!