you need to flash your phone with a chinese firmware (china, Hong Kong) you can use XS++ or SETOOL to flash

XS++ 3.1 Guide-Flashing,Customizing,Recovering - Top Sony Forums
setool2 lite 1.10 - Top Sony Forums

You can use the DCU-60 Cable the one that came with your phone

You need
Main
FS
Cust pack

they are on the download page:

For example:

if you have a CID 52 Phone. You should get a firmware file that looks like:

K550_R1KC001_FS_HONG_KONG_RED52
and
K550_R1KC001_MAIN_CHINA_LI_RED52

Top one is the File System and the bottom one is the main.

they are on the downloads page under (R1KC001_RED52 )

make sure you have and understand everything before flashing =]

Good Luck!