debt legal advice regarding a balance trying to be collected that I do not owe

I am looking for advice regarding a medical bill. I had insurance at the time I went to see my doctor. The claim was never paid by my insurance. The unpaid amount was sent to collection by my doctors office. After contacting my insurance they told me that they have a contract between my doctor and them stating that if the claim was not sent in during the allowed time frame that the claim would nit be paid and all liabilty that me the patient would have to pay the debt would be errased. Basically I would not be held liable to pay because the doctor screwed up by not submitting the claim correctly under there contract. So this takes me too my question. The doctor sent the bill to his attorneys to collect. Isn't that illegal and in violation of his contract with the insurance company. What can I do to protect myself. Last if the doctor didn't know that is why the claim was denied or not paid shouldn't they have done more research into it. Why do people have insurance if the billing department for doctors and insurance companies are doing there jobs correctly. I am upset over all of this because mistakes that were not mine are preventing my doctor from providing treatment to me. - Is this your question? Add additional information