How to unlock Samsung Galaxy S3 T999 with Z3x box

The following is a guide to unlock the T-Mobile Samsung Galaxy S III with Z3X box. I have verified the steps below it worked for me. It's not easy to get it right because of lack of information available elsewhere.
  1. Connect Z3X box to PC via USB.
  2. Enable USB debug on the phone.
  3. Dial *#7284# on the phone, choose Quadcomm USB settings -> DM + Modem + ADB
  4. Connect T-Mobile Samsung Galaxy S 3 T999 to PC via a different USB port.
  5. Select model T999 in samsung tool 13.1.
  6. Select the USB port and then click unlock. The phone will reboot itself after unlock is done.
  7. Congratulations, now you have just unlocked your T-Mobile Samsung Galaxy S3!
To verify whether it's unlocked or not, just pop in a sim card from another carrier (for example, AT&T), and reboot the phone. If the phone is not unlocked, it will prompt you for unlock code upon startup.
Does it work for you? Please leave a comment if this helped you unlock your phone.