Contact the family court services and ask them for assistance. They should be able to direct you in the appropriate course of action. Otherwise, there are usually (in CA anyways) a variety of online forms you can file (along with instructions) to deal with your situation. For contempt (visitation interference) they would typically set a court date within 30 days. You go. You fight. You win or lose. You curse the system. At least, that's what I do.