Find "Network Mode"
Press the menu icon.
Press Settings.
Press More....
Press Mobile networks.
Press Network Mode.
Select network mode
Press WCDMA only, GSM only, WCDMA (preferred)/GSM or 4G (preferred)/WCDMA/GSM.
3G (UMTS) or 4G (LTE) enables you to achieve higher data speeds than when using 2G (GSM).
If you select WCDMA only, your phone can only connect to 3G networks.
If you select GSM only, you can't achieve high data speeds.
If you select WCDMA (preferred)/GSM, your phone automatically switches between 3G and 2G provided that you're within range of a 3G network.
If you select 4G (preferred)/WCDMA/GSM, your phone automatically switches between the three network modes provided that you're within range of a 3G or a 4G network.
If you select WCDMA only, your phone can only connect to 3G networks.
If you select GSM only, you can't achieve high data speeds.
If you select WCDMA (preferred)/GSM, your phone automatically switches between 3G and 2G provided that you're within range of a 3G network.
If you select 4G (preferred)/WCDMA/GSM, your phone automatically switches between the three network modes provided that you're within range of a 3G or a 4G network.
Exit
Press the home icon to return to standby mode.