I went to this place for regular check up of my so...

I went to this place for regular check up of my son. Before appointment I gave my insurance details and specifically asked that please check my insurance and let me know if there are any charges for visit. One regular check up is free and they verified with my insurance. I do not have any complaint with doctors but with the billing, to my surprise i got a bill from the lab. As it turn out Allegro did not send the tests to correct lab which was covered by insurance. This is totally their billing fault. Called them i can say infinite times, But they are not owning up the their mistake!!! Now I am left with no option but to get defaulted on this bill. I irony is, I have no where to go, there is no Government agency where I can go and put my complaint !!! Plz let me know if there is any agency, where I can file complaint and someone can listen to me. I would recommended to stay away from this provider. Imagine you have a billing problem which is caused by them and then you end up paying ?? In my case it is small, what happens if it is big??
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I had issue with billing only, and they fixed the billing issue so I am changing my rating to 4*