I argued several times with different doctors

First, ask them to explain the bill. You could also consult your health insurance. If you think their explanation isn't reasonable, write a letter to argue your points (A letter is much more formal than a call or email). If they don't reply or don't provide good reasons, write again saying that you'll complain to the Better Business Bureau.

I've won 3 times by doing the above. Of course each time I'm confident about my argument.