Job interview advice?

after finally quitting my job, ive applied for many new ones, and never recieved a reply. Recently, I got an email from Big W, inviting me for a group estment interview wih a scheduled date. I was so excited, and really wanted the job. I checked my diary, and realised the date the interview was set for, was while i was going to be away on school camp. I have already paid for the camp, so not going isnt an option. Ive tried to contact Big W, although the address from which they sent the email is unattended, and I cant call the store to which I got the interview, because it is new and hasnt opened yet. I havent tried calling another store, but I would ume they would just say there is nothing they can do about it as it is a different location. I really want this job, what can i do?