Have him prosecuted or not?

She may be your best friend... but its obvious, your not hers if she deleted. You must know, or know of the other woman he is calling. Maybe you should talk with them and see what they have to say. They may not know who is doing it and how to stop it. I would bet he blew your best friend full of s*h*it and she believes him and not you. If it takes having the cops get involved, so be it. one good thing, if he gets arrested he only gets one phone call, after that he won't be calling.