What should i tell them?!?

my ex boyfriend wont stop prank calling me late at night and it gets so annoying! why cant he just get over himself! i keep telling them to stop but they wont!! what should i do?!?!?! i always think i`m over this whole thing with him treating me like this cause we used to be friends, but whenever he IMs me or calls me saying rude stuff and pretending he`s other people with his friends, i just feel like cr*p because of whats happening.