Psychiatrist Office Is Trying To Charge Out Of Office Rates 1 Year Later

Hi everyone.
I'm here because a friend is in a pickle and so far nothing we've tried has helped.

A psychiatrist office claimed to be in network for services rendered last year. My friend paid her in-network copay, and ended up dropping the psychiatrist because she just wouldn't do her job. She made my friend contact pharmacies on her own, do research, all the things necessary to find a place to get her ADHD meds. She would constantly be unresponsive and had to be reminded numerous times to do anything. Eventually, her psychiatrist completely ghosted her, which is medical negligence. There was no proper termination process.

Now, my friend received a bill for $400 because she was told her insurance did not pay the rest of the bills. Turns out they are "in-network with the insurance but out of network for my friend's specific plan" ???

We've tried speaking to the provider, provider's office, billing department, and even the owner, and insurance company, and no one is budging, despite being told this screams fraud, malpractice, and negligence, and that this is an easy lawsuit.

This violates the No Surprise Act, and even worse, her insurance apparently was charged and rejected it, telling the provider to go charge my friend directly. No one is rectifying this situation and we are being dismissed left and right. We've asked for things in writing/email, license numbers, and have been shrugged off.

What do we do here, other than lose more money than this is worth on a lawyer?

Appreciate any help.