I purchased the 16gb IP4 on Tuesday and so far I love everything about it (even with the antenna problem I have). I would like to upgrade to the 32gb. My gf wants to take over my 16gb and go buy a 32 gb for myself. My question is, if I wanted to switch my number from the 16gb to 32 gb once she buys it do I need to get a new sim card? I haven't downloaded anything on the 16gb yet besides my contacts. I was wondering if it would be possible to switch from 16gb to 32 gb between the two of us? If so, do I need a new sim card for the 16 gb?