I know that the sim cards are different sizes and I've seen how people make an adapter to fit the smaller 4g sim into the 3g but I'm just wondering about settings or software compatibility. I broke my iPhone 3Gs while riding my ATV. It was just the glass and LCD but I wanted to get a new phone anyways and got the 4GS. If it's possible to simply transfer the sim card from one phone to the other with an adapter I will fix the screen so that I can bring my old phone with me when I do activity's which place my phone at higher risk of damage. Alternatively, is anyone aware of any other "cheaper" phones which will accept the 4g sim card? If it matters I'm in Canada on BELL. Thanks!