He admitted he was wrong...so why did he go and do it again today?

Boyfriend hung up on me last night when we were talking on the phone, he got mardy and couldn't be bothered with talking after i said he's acting like he doesn't care about some stuff. This morning he texts me saying he's sorry and he was being a **** and he just wanted to drop the whole thing. Didn't talk for the rest of the day and then tonight he's called and the same thing has happened all over again....i just get so annoyed with him hanging up on me, why can't he talk to me like an adult? He's 27! We've been together for 3 and a half years and we're getting married, i want to be able to talk like adults about things that are bothering us and not be hung up on, and to have him say sorry for the way he was and then repeat his actions...he's clearly not that sorry is he!