I don't want to go on a trip and I want to get it cancelled
Is there some kind of problem with the trip?
Yes, there is. My friends are being selfish.
You shouldn't ditch your friends. The trip was planned, so you should go on it. Don't back out.
It's not my fault they can't keep their promises too.
I believe it's best to just go on the trip, because it would be harsh to cancel everything when everyone was looking forward to it! Maybe you'll actually come to enjoy the trip and their company!