The 9.7" iPad Pro has an embedded Apple sim that can support many different carriers. My understanding is that the embedded Apple sim is used if no sim is present in the sim tray. With prior iPad models that shipped with an Apple sim in the tray, AT&T locks the sim to its service if AT&T is activated. This renders the sim no longer usable with other carriers after leaving AT&T: http://recode.net/2014/10/24/att-co...twork-but-says-switching-carriers-still-easy/ Will the embedded sim be subject to the same problem? If an iPad Pro 9.7" is used with AT&T, is it no longer possible to use other carriers without an additional sim in the tray, even after leaving AT&T?