A contractor I hired did not pay one of his subs. The job was completed and we closed out payment with our contractor. Unbeknownst to us, he had subbed out part of the work, and never paid the sub. The sub has now sent us a notice to lien. We called the sub and they explained they have not been paid for their work and the contractor has been dodging them. Contractor is also not responding to us. What are our options?