$850 charged for immunization

I understand that I am partly to blame here as I didn’t actually understand how amercan health care system works but here is the issue.

I recently moved to US on a job and employer provided healthcare doesn’t kick in until September. In the meantime I took a travel insurance online for emergencies.

I also realized that my daughter is not upto date on her immunization and to put her into a school she needed some vaccinations done. When I called a nearest pediatrician office they said its 100 for consultation and 30 per vaccine if we have to pay out of pocket. All good till here.

On the day of vaccination, I told them that I have travel insurance and wasn’t sure if that will cover. I know I am dumb to do this. But they said they can check and said, it won’t be possible and charged me 100(cash) and got the doc checkup done and immunization updated. Once everything is done, they didn’t charge anything for the vaccine. When checked with front desk, they confirmed nothing to pay now. I assume maybe I will get a separate bill in mail.

Today I received an Explanation of Benefits document saying that the patient is responsible to pay $850 with three line items

New patient intake $230

Hep B vaccine $570

Developmental check $50

I am shocked to see this in my mail and am planning to go talk to the clinic on why they sent it my travel insurance when they explicitly said it doesn’t work. And all other charges that they mentioned were not discussed earlier.

Any suggestions on how to tackle this situation? How do I approach it and who should I talk to first?

Sorry for the lengthy post, wanted to give as much info as possible before I forget. TIA.