Are all NYC deli standardized between different owners or does somebody own most of them

hi guys, so i booked a dentist from zocdoc last month and made sure that they were in-network with my dental insurrance. I then received a text / call telling me to book with them directly and they cancelled my appointment via zocdoc. same address and all so I figured it's fine.

I rocked up and signed my forms, I asked them if my insurance covered everything, they verbally told me there was nothing to worry about. I got my cleaning and 1 cavity done, they told me everything will be covered so I walked out without paying any cost.

now a month later i see that they've made a claim via Aetna and they turned out to be out of network and want me to pay 50% of the total cost. which is half a thousand dollars. what do I do now?