You need to stand up for your and your son rights. They do these things and hope that you either do not know the law or do not have the stones to stand up to them. ihashblox already gave you the information you need. Please do not let them stamp on you or your son. Bring this up in court at the next hearing and bring the letter with you. Let the judge know what is going on. Better yet send a personal letter to the judge with a copy of their letter so even if they try to hush you in court you know the judge saw it. You do have the right to send a personal statement to the judge. Be nice and honest yet brief.