i had to get two wisdom teeth extracted. before i went to the oral surgeon i let them know my insurance provider. it's an out-of-network provider. they called me back and told me it would cost $50 for the consultation, which included an x-ray. so i go in and pay $50 before leaving that same day. during the consultation they tell me it will cost me $123 out of pocket for the surgery, so i go back about a week later and have the two teeth removed. i pay the same day as the surgery. a month passes and they send me a bill for an additional $500! the statement also says that if the payment is late, the statement will be forwarded to a collection agency for further action. i call them about the unexpected bill and their explanation for billing more is that my insurance didn't cover all costs. i told them i already paid the costs they said i would need to pay, the $50 and the $123, and that the additional bill does not seem right. they said they would see what they could do and call me back by next wednesday.
my question is, aren't they obligated to verify my insurance and give me the correct costs up front? seems unethical or even illegal if not. what should i do to fight this? all advice welcome.