Hospital billed me $28,000 for a procedure my EOB says is covered at 90% - six months and counting

Had a routine outpatient procedure done in July. Surgeon was in-network, hospital was in-network, everything was pre-authorized. I specifically called my insurance before scheduling to confirm. They said I'd owe my 20% coinsurance after meeting my deductible, which I'd already hit by then. So I was expecting a bill around $1,200 at most. What I got instead was a bill for $28,000 with a note that insurance paid nothing.

Turned out the anesthesiologist was not in-network, which nobody told me. I didn't choose the anesthesiologist. The hospital assigned one. My EOB shows insurance denied their portion citing out-of-network provider. I thought the No Surprises Act was supposed to stop exactly this. I've been going back and forth between the hospital billing department and my insurer for six months and I feel like I'm getting the runaround from both. Anyone been through this specific situation with the No Surprises Act?