The buyer of your old insurer may well still be liable for your claims--if they bought the stock of the other company, they certainly took on that obligation, and even if the only bought the assets, they likely assumed the obligations and commitments as part of the transaction. And if the new company took your premiums (it's unclear from your question whether your are writing about the old or new company when you write "They took our monthly payments but have not paid our health expenses.") they would certainly have to provide the insurance for which they took premiums. You may, however, need to sue them to get  them to honor their committments: consult with an attorney, who can look into the situation and help you understand and obtain your recourse. Good luck.