Medical billing....insurance...... is no different than any other business.
I remember after one of the hurricanes/Noreasters people hiring crane service to get there boat out of the parking lot after breaking from thier moorings. If you didn't have ins and were paying cash it was like say $500 with ins $4000....
We got a new dentist this past year, and the hygienist told me I needed scalings. Scalings are covered under our insurance. I had the scalings done, and about 6 months later got a $585 bill from the dentist for the scalings. Called the dentist and they had put it in again. This went on for a couple of months, then the billing woman at he Dentist told me to call the insurance and complain. I called the insurance and they told me the Dentist office lacked the evidence that I needed scaling based on the notes so they were refusing to pay.
Long story short I talked to the Billing woman and told her it wasn't my fault that the insurance company felt the dentist hadn't proved a need. I also suggested that in the future maybe they should exagerate the need in the notes. The billing woman spoke to the Dentist and they agreed that I shouldn't pay and they cleared the bill