Don't stand for it, I had to call up Portsmouth to get them to get their butts in gear (only to get rejected in the end, but that was because of my points). It's an irritation to you, and it means they may not be doing their jobs very well. Ring them up again, tell them what happened, don't be afraid to get pissed off. Having said that, only get annoyed if they give you a reason to. They screwed up, if they were going to give you an offer but something happened admin side, you should ring them up and demand that place. If that doesn't work, talk to your parents and see if they'll help you. Don't give up yet!