Lg g2 f320 korean signal problem

[Malek La]

I just usee my lg g2 f320s couple a week. The problem is my network gprs G only.i dont know why i dont get 3g or H. When i enter to hidden menu a select wcdma only. The network can't connect it.realy bad for me to used gprs. When i change my sim to another phone its okay to used
I live in malaysia.can someone help me plesss.