EXIT Youtube →Disable Rotate screen.

Wifi off and Viber On→ Activate 4G

Activate your 3G or 4G when the wifi is off and an app like Viber or chrome is activated.

WiFi Connected → Disable 4G

Save battery life by disabling 3G once it is connected to the WiFi

WiFi Off and Chrome On → Activate 4G

Enable 3G/4G if no wifi once Chrome Browser has activated