BCBS keeps denying my son's weekly therapy as 'not meeting medical necessity' after 8 sessions. He's 11 and was just diagnosed with OCD. Has anyone gotten the parity law to work in their favor here?

I'm trying to figure out what to do because my head is spinning. My son was diagnosed with OCD and a co-occurring anxiety disorder back in February by a child psychiatrist that took us four months to get in to see. She recommended weekly CBT with a therapist who specializes in pediatric OCD, specifically ERP (exposure and response prevention) which is the gold standard for OCD treatment. We found a provider in network, my son started in early March, and he is doing really well. His teacher has noticed a difference, he's sleeping again, the rituals around the front door have dropped from 30 minutes to about 5.

Last week we got a letter from BCBS saying that sessions 9 and onward will not be covered because his treatment "does not meet medical necessity criteria for ongoing weekly intervention" and that "biweekly or monthly sessions are appropriate at this stage." His therapist literally laughed when i forwarded the letter to her. She said ERP requires a high frequency, structured cadence and that backing off to biweekly during the acute treatment phase would basically restart the clock on his progress. She wrote a letter, sent her progress notes, and we filed the first level appeal.

What kills me is that if this was a denial for chemotherapy or weekly physical therapy after surgery the carrier would not be playing these games. This feels like a textbook parity violation. Mental health and substance use treatment is supposed to be covered on equal terms with medical and surgical care under the federal MHPAEA. The reviewer who denied us is not a child psychiatrist and as far as i can tell isn't even a behavioral health provider.

Has anyone here successfully cited the parity law (MHPAEA) in a mental health denial appeal? Do i need to file a complaint with the Department of Labor (we have an employer self-funded plan so its ERISA) or the state insurance department? I dont want to lose the momentum we have on his treatment because a desk reviewer is overriding a treating clinician.