As I bought my iPhone 5 16GB,White in the USA from Sprint, full price with tax,unlocked ,it was excepted to be a global phone. But now I come across with some problems in Chinausing local carrier, everything is working properly except sending text message

Dear AppleCare，
As I bought my iPhone 5 16GB,White in the USA from Sprint, full price with tax,unlocked ,it was excepted to be a global phone. But now I come across with some problems in Chinausing local carrier, everything is working properly except sending text message, and iMessage and Facetime also seem not to work.This is very serious for Apple and me! Will I have the chance to fix this?
I tried all the possible solutions from the Internet, and the Official solution offered by Apple (http://support.apple.com/kb/TS4459), but it doesn't seem to work.
Will Apple help me with this issue? Please do.
Information of my iPhone:
SN:F1*******8GJ

IMEI: ****

MEID: ****

ICCID: ****
My Apple ID account：****

<Personal Information Edited By Host>