visitation with son?

my sons dad repeatedly asks my son to come over on days out of regular visitation hours. He is trying to manipulate and control my son through this. He has told me he will do whatever it takes to get his son and will even come in between me and my BF. He has told me he doesn't need me to take care of my son and that he can do it without me. I have documented proof of this. Tonight he calls, asked if he misses the boys( the gf kids) and if he would like to come over. I deliberately told him earlier today that I took the day off to stay with my son. I feel this is violating court order or influencing my son, or something..what do i do?