I was talking to a guy last night who's from Canada and bought his 3G iPhone there. He was showing me on his phone how he could switch which carrier he wanted to roam off of. He was selected between AT&T and T-Mobile. Is there a difference in software depending on the country you go to, such as Canada and the U.S.? Is there anyway to get the software that he has on my phone? The setting was located on the settings screen.