i have a 2g. i can upgrade to a 3g for 99$. once i get the 3g, and sign a new 2 yr contract, can i then upgrade to a 3gs right after for 199$ ? or will i not qualify. i want to upgrade to the 3g for 99. sell it on ebay for like 450$ then get the 3gs. and make a profit. will this work?