Insurance Fraud?

My husbands ex wife used an old health insurance card on 4 seperate occasions, beginning in January to March of this year. WE just got a couple of payment requests addressed to our home, to my husband. They total a little over $1,500. He and I have always used health insurance from my job, not his. The insurance she used had been cancelled over 2 years ago. Are we supposed to file a police report? We called the billing department and said they will not bill us again, but I want that in writing from them, as this can effect our credit rating. This was intentional fraud and she received free health services she had no intentions of paying for. She has never lived in our home, so it is clear she updated her "insurance information" when she changed the address. I'm sorry if some think this is petty, but this is just the latest in a long line of her antics.