I went through something like that years ago.The best thing to do is to stop talking to them.Also stay away from them. I also would suggest filing a police report against them.It is not hard to accept that once you declare things are over,it really is. They have to deal with the fact that no one has the right to take over your life.
My question to you is are you truly done with him? I have been in your boat it is easier to end your situation than you think. Have you ever thought that maybe you are the reason why he won’t leave you alone because you are leading him to believe that you don’t won’t him to leave you alone. Allow me to explain weather you think it or not you give off the vibes that you still care simply by your reactions to the situation. My opinion first thing to do is sit him down face to face so that he can see in your face that you mean what you are saying to him. Tell him that you don’t want this relationship any more without the anger that way when you show him, he’ll know you truly mean it. Whatever you choose to do don’t express with anger because believe it or anger is a sign you still care. I don’t know you, but I can tell that you are angry simply by the way you stated this question so I can only imagine face to face how that looks. If you really want to end this, you really don’t need my opinion I believe you will know what to do it will come to you.