I'm currently using iPhone 4S through T-Mobile but I recently got to have an unused iPhone 5 device that has not been registered in any other network (i.e. AT&T, Verizon, etc).
In this case, what are the steps that I need to go through in order to receive a nano SIM card from T-Mobile? Do I need to update my coverage plan? Is it allowed for me to bring an unregistered iPhone 5 and ask T-Mobile to register the new device for me?