http://www.apple.com/iphone/specs.html http://www.apple.com/iphone/specs.html shows that the iPhone 4S has the same GSM bands as the iPhone 4 (T-Mobile 3G uses

http://www.apple.com/iphone/specs.html http://www.apple.com/iphone/specs.html shows that the iPhone 4S has the same GSM bands as the iPhone 4 (T-Mobile 3G uses the 1700 Mhz frequency, which no iPhone supports). The "world phone" designation refers to the fact that the iPhone 4S has a dual-mode CDMA/GSM radio.