Under Anesthesia

I got a bill from a doctor I never heard of. When I called to find out if my insurance was billed I was told that my insurance company had rejected it. Evidently they find the service (a radiologist reading an x-ray) to be unnecessary and this service does not meet the requirements of my benefits and is excluded from coverage. I am then told I am not responsible for this charge unless I agreed in writing to be responsible for the charge before the service was given. Evidently, I signed such a waiver while under anesthesia.