Not fair

I really hate it when my parents break promises. In one of my previous posts, I meantioned about trading my cellphone. I was supposed to trade it today, and my parents promised on it. I even asked if the money was prepared and made sure that it wouldn't be a burden on them. They kept assuring that it was fine. And guess what? They didn't keep their promise! It's really annoying. I'm kinda angry now...