Hello, I am changing my Motorola Atrix to a device Windows Phone 7 - (I'll buy the new phone on eBay, so it will not be through AT & T). The Atrix 4G has Windows Phone 7 devices and AT & T do not. I wonder if the SIM card can operate the device Windows Phone 7, and if you do not and I have to go to the store of AT & T, upgrade my contract. That would be annoying.... Thank you!