Military insurance

Since being married to my spouse who is in the military I’ve gone to the dentist in 3 cities and gotten my teeth cleaned and any fillings I needed. Every time we moved to a new city I would ask MetLife insurance for a list of doctors on the area that accepts our military insurance and they always email the list to me. So last year I went in for my normal cleaning. Now debt collectors are calling me saying I owe over $200. I never had to pay this in any of the other cities we were in, because the military covers simple things like, regular cleanings and fillings, which is all I’ve ever gotten. So the debt collector lady said that she checked and the dentist office didn’t bill the insurance company like they were suppose to. So because they messed up and didn’t bill the insurance company, I have to pay. 🤔