why would he act like this?

Hi ENA,

so I broke up with my boyfriend about a week ago and we got back together because he promised that he'll change. During that time I was chatting with a guy who I used to flirt with a year ago. He also recently broke up with his gf. I was just talking to him, I didn't have any intention on flirting with him because a year ago, he chose to be with this girl who just broke up with him. While we were chatting, he would say stuff like how much he regrets he chose to be with the other girl and I would reply to him like he never made a choice because I never liked him. I also told him that my ex and I split up at that time, that's why I was lonely and thought that I liked him. So recently I got back together with my bf and I think he was also trying to get back with his gf. I write some statuses on my messenger about how I miss my bf because he's currently back in my country. Today I log onto my messenger and I accidently clicked voice call and I end the call right away and told him it was a mistake. He said don't do it next time, otherwise I'll block you. I told him see if I care and he said if you dare doing it again. So i called again and ended it again on purpose and told him I did it. Then he said bye and I said awesome, I've been waiting for that day. Then he blocked me. I unfriended him on Facebook. I don't understand how he could be so juvenile. Why would he do/say such things. Honestly I don't care but I'm really surprised how people can be so stupid sometime.

sounds like you don't need to be with this guy, at all.

This all sounds a bit childish, honestly. If you were flirting with this guy, it makes sense that he'd start to get invested in that and then be standoffish.