Network Settings

IOS

ANDROID 

Settings
Step 1 From the homescreen, tap Settings

Step 2 Tap Cellular

Step 3 Tap the 2G/3G (Auto) or 2G/3G/4G (Auto) connection
Step 1 From the home screen, tap Apps

Step 2 Scroll and tap Settings

Step 3  From the Connections tab, scroll and tap Mobile Networks

Step 4 Tap Mobile Networks

Step 5  Tap Preferred network mode

Step 6 Tap the preferred option. Select 2G/3G (Auto) or 2G/3G/4G (Auto)

Step 7 Tap OK to apply the new settings.