Any unlocked
GSM phone with the 850mhz and 1900mhz bands will work in the USA with a
GSM provider such as Cingular or T-Mobile, but it will only work as a phone until you configure the data settings. In most cases, this is easy to do, but sometimes with foreign phones it can be tricky to find the right settings. Korean
CDMA phones will not work in the USA, they are actually WCDMA, using RUIM cards (the
CDMA equivalent of
SIM, not used in North America). It will be a number of years before a Korean
CDMA phone can be used in the states, as it will require a complete restructuring of every US
CDMA provider's network.