Well, I don't really know what to say to that. Is there anything about him that genuinley interests you, whether it be as a potential friend or even boyfriend? If so, then I would personally give him another chance. Everybody makes mistakes. I would give him another chance and if he continued to cancel plans like that or even did other constantly annoying stuff that could easily be avoided, then I would say that he's either messing with me or that he just doesn't care as much as I thought and hoped, and then just try to move on. I understand how much that must've upset you, but you never know. If you don't know this guy very well, then I would really suggest giving him another chance. Even if it doesn't work out as being "boyfriend and girlfriend", you might just gain another good friend!!
Also, just a little advice on something else. I noticed how you said that sometimes you "try and be interested". It's okay if you're not interested in someone as a potential mate. You shouldn't have to try to be interested. There's nothing wrong with talking to people and being polite and maybe even becoming their friend, but being interested in them as a potential mate is something that should come naturally when you meet someone. Things take time of course, but even throughout that time, you still shouldn't have to try. As time goes on, it should come naturally. I mean, I would always give people a fair chance and keep in mind that friendship is always a good thing (if things don't work out beyond that), but don't ever settle and don't ever TRY to be interested.