Exactly as LCRT stated above - unfortunately there is no way to "speed up" the firmware update availability by "unlocking the phone" or changing the SIM-card.
Need clarification please. Are you saying the Firmware update for my Unlocked Dual Sim 950 is dependent on AT&Tls interaction as LCRT post suggests in this statement "No. unlocking the device to other networks does not change the fact that the FIRMWARE is branded by AT&T, and it is an AT&T product. unlocking achieves nothing." or is the Firmware Update dependent on Microsoft's rollout schedule and nothing else?