I had similar thing happened before. my doctor changed

lab one year and it was a out of network lab. the routine blood test was charged thousands of dollars. I called my doctor's office because I had no idea they changed their lab and caused all of this trouble. My doctor's office negotiated with the lab and insurance company and finally took care of the billing issue and I didn't have to pay for it. So I think you start with the doctor's office. If they are decent, they will try to help you.