surgeon was in-network but the anesthesiologist hit me with a $4,800 surprise bill - is this still legal under the No Surprises Act or am i missing something

genuinely confused and getting nowhere on the phone with anyone. had a scheduled outpatient shoulder surgery in march at a network hospital, with a network surgeon. did all the homework. called my insurance (anthem PPO), confirmed the surgeon was in-network, confirmed the facility was in-network, even confirmed the post-op physical therapy plan was in-network. felt like i did everything right.

three weeks after surgery i get a $4,800 bill from "Mid-Atlantic Anesthesia Associates." never heard of them. apparently they were the anesthesiology group contracted by the hospital, and they happen to be out of network with anthem. nobody at the hospital mentioned this. nobody at the surgeon's office mentioned this. there was no separate consent form for an out-of-network provider as far as i can tell, and i specifically remember signing a pile of paperwork at 5:30am that morning while groggy and anxious.

my read of the federal No Surprises Act is that this exact scenario - facility-based ancillary provider who you didnt choose, at an in-network facility - is supposed to be protected. i should only be on the hook for what i would have paid in-network, and any dispute between the anesthesia group and anthem goes through the federal IDR process. but when i called anthem they said the bill is "valid" and i need to "negotiate directly with the provider." called the anesthesia group's billing department and they said "the No Surprises Act doesnt apply to your plan because of how it is structured." nobody will tell me which specific exception they think applies.

has anyone fought one of these and won? do i file a federal complaint at cms.gov/nosurprises first or do i push anthem harder? i can technically afford to pay the bill but the principle of this is making me crazy and i suspect a lot of people in this situation just pay it because they dont know.