Affiliate Marketing Secrets

I recently made a doctors appointment for my child to get a check up and a few tests done. They called me back and said that I owe money on a few past due bills from a hospital that they are affiliated with. As a result, they refused service for my child and said they can only see her if she is sick. While I would understand denial of service for myself (I currently have no insurance), I’m not sure if it is legal for them to refuse service for my child. My child has insurance and the past due bills from the hospital were for services granted to me, not my child. I understand that doctors need to make money, but they are not taking a risk in seeing my child because she has full coverage. Is there something fishy here, or is this common practice?