ghost from the past

My psychotically violent ex keeps calling me once in a while even though I never answer any more. I just can't have someone like that in my life in any way, shape or form. He was leaving messages like, I have a girlfriend, I'm sober but I'm bored. Let's hang out. Eventually as I didn't answer, he would mostly hang up or be like, please call me back at this number. As the months passed he would still call me! It's been since February when I last saw him and he just left me yet another message. I could barely make out what he was saying he was talking so fast. He started with just words: crack, single, pissed off. Let's hang out and have a few joints or drinks if you want. Call me at this number... And I couldn't even if I wanted to because he said the numbers so fast, no one can make it out. I've never heard him so high on crack before. I feel bad for him that he relapsed but also scared. Crack is not good for someone who already normally has violent, unpredictable tendencies. I had to call my dad and warn him to keep everything locked just in case he shows up. Luckily he doesn't know where I live but he still knows where my dad lives and I told my dad just to call the cops if he shows up. And then of course I had a dream where I was smoking up. I think I may have to change my number...