hi, so heres the down low. i want an iphone, and my brother wants a phone all together. right now im on a family plan of five people (maximum), and my dad is on his own by himself. we have unlimited texting, and unlimited calling i think. so what i was planning in doing is giving my current phone to my brother and going on my dads plan and buying an iphone. or would it be cheaper monthly to just buy an iphone and stay on my current plan, while my brother went on my dads? (he'll have no data plan, just text and call) im trying to avoid the 70 80 dollar monthly bill if possible. also im with at&t. thanks in advance