From the home screen, use two fingers to swipe down the Status bar.
Tap the Settings icon.
Note: If only one finger was used to swipe down the Status bar, swipe down again to access the Quick Settings menu.
Tap Cellular networks.
Tap Preferred network type.
Select the preferred option:
For 3G only, tap 3G.
For 4G access (where available), tap LTE or Global.
The 4G connection setting is now changed.