SIAP but I was unsure if any other threads pertained to my exact issue. I currently have a iPhone 4 that is on an account of my own. I am not eligible for an upgrade until April. My mother and father, both 3GS, are eligible on their account. Mom is upgrading to 4S. Father does not care to upgrade to 4S, but will use upgrade to benefit me. My question. After he activates the iPhone 4S, complete with new sim, can we just swap sim cards between my 4 and his 4S, despite being on different accounts? If so, do we hook up to our iTunes accounts and restore from our respective backups (done before switching)? Thanks in advance for advice/help.