I believe that StraightTalk (http://straighttalk.com http://straighttalk.com) piggybacks off the AT&T network. However, they might not like you using that much

I believe that StraightTalk (http://straighttalk.com http://straighttalk.com) piggybacks off the AT&T network. However, they might not like you using that much data. American carriers generally restrict which devices you can activate on which plans in order to guestimate average data usage for that device. For example, Sprint charges an extra $10/mo for unlimited smartphone data over the unlimited data for other devices. So, StraightTalk might decide to disconnect your device if you use "too much" data and aren't using one of their devices. I'm not saying it's right to put restrictions on "unlimited data", just that they might decide not to serve you as a customer using a device they don't sell (and it might mean that you have a $650 iPhone that you can only use on AT&T). It's also possible that StraightTalk doesn't rent 3G off AT&T. So, it might still just be 2G. For example, Sprint roams on Verizon, but doesn't roam on Verizon 3G, only 2G (except in former Alltel areas). It should also be noted that over 24 months, the unlocked iPhone will cost you an additional $18.75/mo. So, you'd have to find a discount carrier that was a lot cheaper, not just a little bit cheaper. If you expect to upgrade your iPhone every year ($37.50) or 18 months ($25/mo), the unlocked's pricing starts looking worse. So, make sure to think about that too.