AT&T for some reason keeps telling me that there are no differences in the SIM card used between Iphone 3GS and Iphone 4. On more than one occasion even though I keep telling them it uses the micro SIM now. I've done some searching and found a little info but I can basically just cut my 3GS SIM to fit? I'm doing an upgrade swap and it would be much easier to just pop the SIM from my 3GS in the new phone rather than deal with AT&T and switching numbers around because of the SIM cards. Thanks and sorry if I missed this in a search.