I am on RW, and use a Motorola Defy XT, I just got a Moto X that was also used on RW, what do I need to do to switch phones?
Follow the instructions for reactivation found here:
You can follow the steps in this document. If you want your number to move to X choose the replace number choice during activation.
Doing the above will deactivate the Defy and it will not to be able to be reactivated in the future.