Be aware MB phones do not work on (PCS) Sprint. Motorola Timeports were available in different formats, TDMA, CDMA they will charge, but not communicate properly if it is a factory install. MB made them do some custom software, I have no idea why, they finally are touting a universal interface.
GSM seems to be global, but only T-Mobile makes it available in the states, you change the SIMM card and roam $ 1.00min in most of Europe.
T-Mobile sort of spotty in US especially roaming.