Find "Network Mode"
Press Apps.
Press Settings.
Press Wireless & networks.
Press Mobile networks.
Press Network Mode
Select network mode
Press GSM/WCDMA (auto-mode), GSM only, WCDMA only or GSM/WCDMA (WCDMA preferred).
3G enables you to achieve higher data speeds than when using GSM.
If you select GSM/WCDMA (auto-mode), your device automatically switches between the two network modes provided that you're within range of a 3G network.
If you select GSM only, you can't achieve high data speeds.
If you select WCDMA only, your device can only connect to 3G networks.
If you select GSM/WCDMA (WCDMA preferred), your device automatically switches between the two network modes.
If you select GSM/WCDMA (auto-mode), your device automatically switches between the two network modes provided that you're within range of a 3G network.
If you select GSM only, you can't achieve high data speeds.
If you select WCDMA only, your device can only connect to 3G networks.
If you select GSM/WCDMA (WCDMA preferred), your device automatically switches between the two network modes.
Exit
Press the home icon to return to standby mode.