My family is on an existing At&t family plan and I'm going to upgrade to an iphone 4 from my current iphone 2g. My dad on the other hand wants an iphone but he has no use for internet and does not want to pay monthly for the data plan. Right now I'm the only one on the family plan with a data plan, my dad's sim doesn't have data plan. I'm planning to give him my iphone 2g or buy him an iphone 3g or 3gs on craigslists. I was wondering if he put his sim card into my iphone 2g or into iphone 3g or 3gs, could he use it without paying for the data plan? I'm having a hard time figuring out how At&t would even know he's using an iphone? Also would jailbreaking or unlocking it make a difference? I've read in a previous post that redsn0w would bypass the forced data plan and only iphone 2g remains undetectable allowing you to use it without data plan. Can anyone confirm this?