Read help info
You can limit your data usage by turning off mobile data. You'll then not be able to access the internet using the mobile network. You can still use Wi-Fi even though mobile data is turned off.
Turn mobile data on or off
Press "More" below "Wireless & networks".
Press Mobile network.
Press Mobile data to turn the function on or off.
Return to the home screen
Press the home icon to return to the home screen.