Press the Menu button and Scroll to Settings, Press SELECT.
Scroll to "Other Settings" and Press SELECT.
Scroll to "Network" and Press Select.
Scroll to "Network Setup", and Press SELECT.
On Band, Press CHANGE.
Scroll to and SELECT the frequency of choice. (1900 for North America, 900 for China and 1800 for Europa).
Press DONE.
Now your tri-band phone can use in China. You may give it to your family or friends as a gift, tell them just change SIM card.