I had a water leak and called a mitigation company to mitigate the leak. I did not sign any contracts or agreed to any payments. They sent me $9000 invoice for the work. I submitted it to my insurance company who states that the mitigation company has overcharged me. They will not pay for certain costs as they are not "industry standards." I have had other people look at the invoice and they all say that some of the charges are not accurate. I don't agree with some of the measurements that they used to come up with the charges or some of the hourly charges that they billed for. I have offered to pay them what I think is fair and reasonable. The mitigation company is threatening to put a mechanics lien on my home. I have offered a settlement amount of $6000, however, they do not want to accept that. What can I do?