How do my parents handle disputing a debt from an unlicensed contract?

My parents hired a guy to do work from a tree falling on the home and we found out that contractors are unlicensed and the biz is also unlicensed. He was asked at the beginning if they were licensed, insured and bonded and he said that he was and would provide said docs when the sign contract. My parents never saw proof of this. From the beginning he had them sign a contract with him for assignment of benefits and direction of Pay, working directly with the insurance company. We had to hire a PA (public adjuster) because insurance was dragging and still are. This has been going on since November. We found out that the entire house contains friable asbestos and the contractor argued that he would do the job, we found out that he was not licensed around this time and sent a cease-and-desist letter in early December. sent a cease and desist and now the unlicensed contractor has hired a law firm to collect and exorbitant debt, in which they had not even fulfilled. They had already been paid 59,089 dollars for tree removal, tarping the portion of roof damaged, demo of one bedroom and removal of gutters and downspout. No repairs have been made. They ripped out all the carpet in the home and we found out outward. They are asking for us to 22,000.00 for roofing repair and etc. Which has not been done.