I lost my phone...how can i get a different one?

OK...well I was in school today and all of a sudden i couldn't find my phone. I told my dad and he shut off the phone...but he said that I have to go look for it in school tomorrow. I'm bound to not find it, so I looked at the AT&T website today and was looking at the BlackJack 2. I want to know if I can get the BlackJack if I had a Razr V3 before and pay the difference even if I'm still in a contract for about 9 months. Oh...and how much does a BlackJack 2 really cost...Thanks