My general contractor hired a subcontractor to do the plumbing on a remodel. I was unaware of him and after the work was completed he claimed he was not paid enough and will file a mechanics lien against my property. He did not file a preliminary notice or have anything in writing it was a verbal agreement with the general contractor. I filed a notice of completion with the county clerk and served my general with it. Also posted the property. What can I do to protect myself?