I want to hand down my phone or basically swap phones with a family member. We have a iPhone and non-smartphone both under contract on the same bill. Can we just swap sims and go on about business and our numbers would switch that way or can we not do this? Would it effect our upgrade dates, we are still fulfilling the contracts so I'd hope not? I'm hoping to eventually ditch the basic phone for the iPhone 6 once the that's out and my contracts up on one of the lines but don't want to mess with anything if I switch numbers.