If the iPad comes with the pre-installed Apple SIM card, AT&T will lock it to AT&T, but swapping out the SIM card should be all you need to do to use the iPad with another carrier.I bought iPad Pro 12.9 through 3rd party and is wifi & cellular and states it is for AT&T. I have heard that all iPads are unlocked and can be used with any carrier. Can anyone verify this.