Is ex-wife calling too much while Son is with me?

During my periods of possesion, my ex-wife is calling every night and sometimes every morning and every night. Our Son is now 7yoa and seems to become disconnected from me for a short time after the calls. The last 3 weekends that he was with me, I have not taken her calls. I tell my Son that she called, that she says she loves him and that he can return her call if he wants(he never does). Our time togethor has been so much nicer. He is better disciplined, has a stronger appetite and seems generally happier. I don't know if it's just a phase or if it is related to the non-contact. Maybe, he can focus on US without interruption? I've adopted the same policy while he's with his Mother. I tell him that I'm available anytime if he wants to call. At his age, there's not much of a telephone conversation, anyhow. Are there any resources that would confirm this theory? I'd like to address her, but she's very overbearing and will deny my ideas. Whatcha think?