A contractor and I agreed to certain work at my house for $900, which I paid him in three progress payments of $300 each. During the original project I asked if he would do some additional things, which he did, and I offered to pay more but he never asked for any additional money. Before the original work was finished, though, he walked off the job and demanded more money, leaving a huge mess and the incomplete project. Now he’s threatening to file a lien, but we never had a written contract and he never sent me any invoices for the original work or the additional work. If he does file a lien how can I get it dismissed?