Hey guys, so just some quick background: I have an iPhone 4 on AT&T. My sister is getting it though so we ordered a 4S through her number and I was just gonna switch phones with her. When the 4S does come, can I just put my sim card in from my old iphone 4 before I turn it on and just set it up like normal. My dad for some reason is convinced that the phone's are locked to the SIM's IMEI number or something unless I go into the store, but I'm pretty positive that's not the case. Please let me know!