The National Consumer Law Center recently published an article on medical debt as part of their Consumer Advice series. They encouraged readers to share the article, so here is a link: https://library.nclc.org/dealing-medical-debt-consumer-advice-nclc.
In brief, the article essentially says that you should ask about financial assistance or try to settle the debt through payment plans. The article also mentions that you can defend the debt based on the argument that the charges are unreasonable. I think that is a good starting point.
However, I have addressed additional strategies for defending medical debt claims.