My wife and I currently have the iPhone 3G.  We are planning on upgrading to the iPhone 4, probably in July.  Our children have old POS phones without any data plan – just voice and text.  The son’s phone (Motorola)  has very poor quality and it sounds like he is talking underwater.  The daughters phone (Pantech Duo) is temperamental at best.  It shuts off by itself or the screen goes technicolor and she cant see the screen.  Our son is currently in the Delayed Enlistment Program, due to ship out sometime within the next six months.  Our Daughter will be signing up for the Delayed Enlistment Program next month and will ship out about this time next year.  I don’t want to replace their phones and get locked into another two year contract when they will be out of the house long before that two years is up.  I don’t want them to sign up for their own contracts right now because they have no idea where they will end up.  If they end up somewhere oversea’s, the A.T. & T. contract will be worthless to them.  What I would like to do is when we upgrade our phones to the iPhone 4, give them the iPhone 3G and just let them use it as a phone (and iPod).  We already tested their sim in it and it works.  If they attempt to go somewhere (data-wise) it comes up and says a data plan is not approved for this account (I’m paraphrasing).  If they need a data connection, it works fine when it is on WiFi.  My concern is this:  Can A.T. & T. tell what kind of device is on a certain sim?  And if they see it is an iPhone, even if the data apps are not being used, can they force the data plan on to my bill?  If they can, and they do, would that extend the contract on either of the kids numbers?  I would like to be able to help out my kids in the most economical way and without extending a contract since they will be on their own before it is too far into it.  My only other option is finding a decent used phone on craigslist, but that is dumb if I have two perfectly good iPhones they can use.  Has anyone ever tried this and what was the outcome?  Thanks  Jim
