Need help of Sony Ericsson Z800i network

I can not calling or receiving the voice call when using Z800i. I only send the SMS masseges. Using another SIM type could call as normarl, and I using this my own SIM can not, change to another phones was normal (not SIM mistake).
Thanks and hope received the best help
email: halongtraseco@hn.vnn.vn

[KidoBorg]

Go to the nearest offices of your wireless provider and let me know what is going on. They should be able to fix it.