Big Springs Dental Clinic

They ran my insurance out for the year (which pays 1000 dollars on dental work per year). On three fillings. Two of which have failed and they refuse to give me any sort of assistance or refund for further treatment. Now they are sending me a bill because the insurance wouldn't pay 400 dollars for a filling (which I paid 70 cash on at the office as my portion.) never doing business with them again. When did a filling cost as much as a root canal?