Does anyone know how the process works if I purchase a iPhone 6 Plus through Apple & want to activate it on my existing line? I currently have a iPhone 5s & I am looking to purchase the 6 plus through Apple..so I am wondering if I can simply swap phones by activating the new phone on my current line or will there be fees and or changes made to my plan? Also do I need to be eligible for an upgrade in order to purchase the 6 plus through Apple? Thanks!