Is it ok to be mad, because shes still calling him? Would it be ok to confront her myself about it?

Ok... so my boyfriend and I are engaged, so he is now my fiance and we will have been together for 6 years in August. Unfortunately, his ex-girlfriend/first love still calls him occasionally. In the beginning of our relationship I had no problem with it because i knew they were just friends, after 2 years it became annoying, and at the 5th year i wanted him to cut it off because i thought it was ridiculous. He hasnt seen this girl in at least 4 1/2-5 years and he never made any attempt to call her. He could see that i was annoyed with it, so the next time she called, he told her that I was bothered by her still calling and that she needed to stop ( this was about 6 mos. ago), and she got really mad and left him a nasty voice mail message later on. I thought that it would be over with, but she occasionally still calls him and leaves him messages about her life story, because he doesnt pick up anymore. I want to pick up the phone the next time she calls and end it once and for all. I do not want to be in my 50's, 25 years later, and her still calling once or twice every couple of months trying to talk to my husband. However, he would prefer i not cause any drama. I respect his decision but im really annoyed and it severly bothers me for a couple hours each time she calls. What should i do?