I have an iPhone 2g and I am eligible for an upgrade from at&t. I was planning on getting a 3gs but I'm hearing cool things about the 4g, so I thought maybe I should wait. But I don't know if my 2g will make it. It's seen better days. So if I get a refurbished 3g or 3gs will that use up my upgrade from att or will i still have it? thanks