I'll just put it this way - If the doctor's office were to take you to court to get you to pay this bill, they would win. Plain and simple. Just because YOU didn't know that it was a separate charge, does not mean it's not valid. You could have asked if it would be a separate charge, you didn't. You signed an agreement to pay whatever your insurance designated as your responsibility. You agreed to let him treat your problem. Pay it and quit whining. Next time ASK FIRST.