Doctor I’ve been seeing entire pregnancy is suddenly out of network so I got charged for the delivery

First, my insurance is Cigna and I have the “open access plus” plan if that matters. Since the start of my pregnancy in Sept, I picked an in network OBGYN and hospital and everything was going smooth. I gave birth a couple months ago, they paid the hospital bill and I thought all was said and done until I got a notification that a $12k claim was denied last week. While the $45k hospital bill was paid, Cigna denied the claim for the doctor that performed the c section – the same one I’ve been seeing for 9 months with no issue, and the reason was “out of network”. Huh, I saw that doctor for a routine check up 5 days before and that claim went through, so I thought it must be a mistake?! I checked Cigna’s website and app to confirm, the doctor was in fact still listed in network.

So I called Cigna and the agent advised the contract with the doctor ended a month earlier and they must just not have gotten around to updating the website, so the doctor was out of network now and that next time I should call, not just rely on their site, to confirm before I receive care. Seriously? Oh, sorry for not phoning in before being wheeled in for an emergency c section. Also, every time I went in for a visit I was asked by the receptionist if I still had the same insurance. I’m assuming at that time if they were now out of network I would’ve been told. So I also called the doctors office and they were confused saying on their end they show they still take the Cigna plan I have. Yet now I have a $12k bill from them that I got in the mail today.

My questions are

Even at this moment, Cigna still lists the provider as in network on their site and app. The doctors office also still claims they are in network. So even if I checked on both sides, how would I have ever known they’re out of network?!

The hospital gave me a flyer when I checked in that I dug up called the “no surprises act” where I’m supposedly not allowed to be billed if an out of network provider performs a procedure on me at an in network hospital. The hospital is definitely still in network as that claim got paid. So say the provider is somehow now out of network like Cigna is claiming… would this situation fall under this law? And if so, would I bring this up to Cigna for denying the claim or the Doctor’s office since they’re the ones billing me for the difference?

Cigna says they put in a ticket to see if their claims dept would “grant an exception” due to the error on their site listing the doctor as in network (which still isn’t fixed a month later). Do I have any course of action to push back more if they don’t “grant an exception”?