OK so my situation is this. I got the 3GS in 09. I'm on a family plan with my dad and bro. My dad has the main line. I am the only person who uses a smartphone. They use flip phones(Razr). My 2 questions are Can I use one of them as an upgrade even though they have flip phones, and never have bought an iPhone? And if I can will buying the iPhone 4 through them result in another monthly data fee being added to the acount?