Discovery doing all in it's power not to pay out a claim

Discovery health not willing to pay and ICD 10 code F90.2 for my son's treatment.

After making several calls of over 50 minutes of my precious airtime I was informed that the statements I sent through to *** will not be paid as the ICD code is faulty. I went to the medical practioner and was informed that Good Prognosis is handling the accounts for most doctor's in Rustenburg. Went to the offices of Good Prognosis and they stated that all their statements and invoices look the same and Discovery should pay me my claim is the correct ICD 10 codes ( F90.2 ) is stated.

I also have enough more than enough money in my Medical Savings Account to cover this.

This has been dragging on for 6 weeks now. REALLY getting fed up. I've been with Discovery for 20 years but really consider moving on.