Nef, how often is he calling/texting you?
I wouldn't go straight blocking him, like Cindy said, in a way where he knows it. When I did that to the guy who was stalking me he a. Started physically showing up places and b. his friends all over town started telling him where I was and who I was with any time they saw me. It was miserable. And that guy didn't leave me alone for years.
So I think you either go about it legally or in some way that he's too scared shitless to keep it up. Blocking him just makes him think you're still too weak to deal with him, and makes him think he can keep going.
Hope you find an app or anything that helps.