Once the iPhone 4S is activated on VM, the baseband locks down all the GSM radios making it impossible to use it anywhere but Sprint's native network. Just like the domestic GSM radios are blocked when the 4S is activated on Sprint or Verizon. It's really stupid that they do that too. I just hope that the jailbreakers figure out how to break thru the baseband so they can unlock all the radios, and then the phone could be used on any GSM carrier worldwide.