I was wondering about this too. I plan to buy an unlocked pre2 and give my preplus to my daughter, who has a sim that is restricted to no data use, only voice and text/mms. I think that means she won't be able to complete activation, even here at home over wifi, as you can't get into wifi settings until it has completed activation over 3G/Edge.
Originally Posted by VCI_Cell
What I could find online was that numerous people said it is best to go to an ATT store and discuss in person at the store, as all of the online tools try to sell you a phone and plan package. Many people reported success at the store buying a sim card with a month to month commitment or as a go phone plan. I was unable to find how to buy just a sim card online, except on ebay, and that is sometimes a roll of the dice.
Hope that is helpful.