Fraudulent Dental Bill

Hello all, last year I went to a new dentists for a routine cleaning like I always do every 6-12 months. Now I move around for work meaning that I am always a “new patient” and it is a major inconvenience. Last fall when I went they said they would have to do a new set of dental X-rays before they would clean my teeth. I offered to send them my last set of X-rays and said my insurance probably wouldn’t cover two sets of X-rays in one year. They insisted that it would in fact be covered, so we did it.

Several weeks later I get a call and email saying I now owe $298 because insurance actually didn’t cover my X-rays. I was furious because I explicitly talked to them about this scenario. So from
my understanding, medical bills under $500 cannot affect your credit score. And since this whole thing felt like a scam I refused to pay.

Now fast forward 6-7 months later and I get a letter in the mail from collections. It says that I now owe $498?!? How can the original bill increase? Before I call them I want to know what I am getting into. If the original bill was under $500, which it was, then it won’t affect my credit correct? But if they keep doing shady math and adding arbitrary fees it will now be over that $500 limit. Can they do this legally? Can I ask for an itemized sheet of how this debt now jumper? Do they just charge 10% compounding interest each month and call it a fee?? I’m furious