say you have the iphone 3G and are not interested in using data at all what would happen to your voice calls if you disable 3G in the settings menu? would call quality suffer? or would it not matter at all. reason is because my friend wants to lend her dad her iphone 3g for a few days and he just has a regular voice plan and she doesnt want him to incur any data charges. he would just be putting in his sim card from his old phone which broke. And yes his sim card works in the phone, and no she is not scamming AT&T since she is paying the 3G data plan anyways during these few days.