If notifications are turned on, your phone will use mobile data when applications send push notifications and is not connected to a Wi-Fi-network.
Solution: Turn notifications on or off
1. Find "Notifications"
Slide your finger downwards starting from the top of the screen.
Slide your finger downwards starting from the top of the screen.
Press the settings icon.
Press Apps & notifications.
Press Configure notifications.
Press Notifications.
Press the required app.
Press the indicator to turn the function on or off.
Press the Home key to return to the home screen.