While I am not defending the facility, which was careless no matter how you slice it, I do want to point out something that not everyone knows unless they work with health insurance (which I do, and have in one form or another for decades).
Every major insurance carrier has more than one network, and not all facilities are on all their networks. The major insurance carrier that my employer uses has 22 different networks covering our region, and that's omitting the dental and Medicare Supplement networks. The rate of overlap is probably in the high 80's if not the low 90's, but not all providers are on all networks. One of the things I have to do is make sure employees calling about their health plan options know which network to look at. Most of the plans we offer use (network A) but two of our plans offer (network B) and the student plans, which my office does not administer but which many of our new employees are coming off of, uses network C). This carrier is not at all unique. If I remember correctly, the major carrier that I worked for in the early 90's had 26 different networks.
At the same time, when there are facilities with multiple providers, not all of the providers have their contract with the insurance carrier renew at the same time, and the renewals do not all go smoothly. It is not impossible for any given in-network provider at any given in-network facility, to be temporarily out of network while the contract negotiations are going on.
It is not possible for the facility's receptionist, patient services, or billing office, to automatically know up front which network THIS patient's insurance plan uses, or the status of THAT provider with the plan in question. That's simply not information that they can keep in their heads. If 95% of providers are on 90% of the carrier's networks, and they're juggling the affairs of 25 different patients at the moment the patient in question asks, it's going to occasionally make a mistake. It's not deliberate, it's not malicious, it's not a coordinated plot to make this patient pay out of network rates; it's a mistake.
That is why it is imperative that instead of relying on the facility to say if they are in or out of network, the patient contact the health insurer DIRECTLY and confirm not only that Dr. Jones is in network, but that Dr. Jones is in network while practicing at the office at 123 Maple Street in Anytown. Get the name of the representative who answers and write it down along with the date and time of the call. That will give you much more protection in the event of an error, than relying on the doctor's office call.