Have your doctor get on the phone with the nurse care manger at your insurance company. He/She are the one's who should be dealing with getting treatments authorized for their patients. One thing I found out, trying to deal with the insurance companies can become a nightmare and who needs the aggraviation. The insurance companies are looking to save money anyway they can. Having the doctor or someone from the office be involved helps. I found that out. If they deny you can fill an Appeal.
Wishing you the best of luck