right now, i have the rumor touch and an unlimited messaging plan from sprint. if i wanted to upgrade to a smartphone, i would have to buy a 30 dollar data pack (my parents don't use data, so it makes more sense to buy data for one phone rather than upgrade the entire family plan) but..how does an unlocked phone work? if i buy an unlocked data phone for sprint, can i program it to my number and only buy the 15 dollar data pack from sprint (the one for regular phones, not smartphones)?