Most Helpful Guy
it should be concerning to you not why he doesn't block her, but why he doesn't just tell her to back off.
I think blocking numbers is useless. She will find another way to contact him if she is really that "crazy". I think you should ask him why he doesn't lay down the law with her. If he isn't willing to lay down the law then you should question how over her he is and how much he really cares about you and his current relationship.
Tell him that all her contacting makes you uncomfortable (that is a fair thing to say). Tell him that you would really appreciate it if he addressed the issue with her and told her that she needs to stop texting and calling since he is in a happy relationship. If he says he doesn't want to do that, then you say playfully so we'll just live forever as a trio. You and I together and her texting and calling every day. If he doesn't really how absurd the situation is then he's simply not over the ex and in a indirect was is disrespecting your relationship.
He has to take some step to remove her from his life (at least in the capacity that she is in it now).