Sim card and contacts problem

[geodoc]

I got a new iPhone and want to give my son my 3GS. The guy at Best Buy said I should be able to move his sim card from his 3G to my 3GS and all the info would switch over.

When I move the sim card the 3GS activates but still has my contacts, etc. even though it is his sim card. Help??

 

[P Mentior]

My understanding is that the iPhone doesn't save contacts to the SIM card but to the iPhone itself. If your son has had iTunes sync his contacts with the computer to something like Microsoft Outlook then you could just have iTunes restore the 3gs and select restore from backup and use his backup from the 3g.

Edit: Sorry if that is hard to understand, I'm only working on 4 hrs of sleep in the past 2 days....