You did everything right. You checked that the hospital was in your network. But weeks later, you get a $2,000 bill because the anesthesiologist who walked into the room for 5 minutes was personally "out-of-network". This used to bankrupt people.
The No Surprises Act
As of 2022, federal law protects you from this. If you go to an in-network hospital, but are treated by an out-of-network doctor without your explicit written consent, they cannot legally bill you at the out-of-network rate. They must treat the bill exactly as if the doctor was in-network.
How to fight back
If you get a surprise bill, do not panic and do not pay it immediately. Call the billing department and say "I believe this bill violates the Federal No Surprises Act." 99% of the time, the billing department will immediately pause the bill and reroute the dispute directly to your insurance company.