Can I buy a Blackberry after I bought a iPhone 3G without having to pay retail or a penalized fee?

I do not wish to keep my iPhone 3G anymore and am looking to buy a Blackberry of Blackjack II from At&t. I upgraded from the regular iPhone to the 3G on the day it came out (in July) and bought a new contract with the 3G. I was wondering if I could buy a new phone at a 2 year contract price rather than buying it at retail price or off ebay or something?