About Kids, Cell Phones, and Non Costudial Parents?

My son's father (non custodial parent) bought my son a cell phone for Christmas. This is completely unnecessary. I have never denied access to him. It's an attempt to have control over my son, track his every move and have his overly involded ridiculous family call him all day everyday. They already tell him inappropriate things, and plan things with him without consulting me. I am stuck having to monitor the best that I can the way it is. The things they tell him is that he will be coming to live with his dad, and that he will be going on this vacation and that one etc? What can I do? My son is 11 and slightly Autistic. He has no phone skills either. It's a "court" tactic to "prove" that I won't allow access to him, which doesn't even exist. If I allow this, they will be calling all the time telling him god knows what & tracking where he is everyday. Is there a way to say No?