Getting out of a Army Reserve Contract?

Hello, I joined the USAR in November of 2007. I am a highschool senior and my ship date is July 10th 2008. I did not enlist into DEP I was attached to a Reserve Unit in Phoenix (where I live) and I was alowed to attend 3 drills. I have decided that I do not want to go, If I don't show up for my Ship day, will my contract be voided with no punishment like people in the DEP??