If you want to avoid using data, you need to deactivate mobile data on your mobile phone. Once done, you can only make voice calls, send SMS and use applications that don't require an internet connection.
Step 1 of 6
Find "Mobile networks"
Slide two fingers down the display starting from the top edge of your mobile phone.
Tap Settings.
Step 2 of 6
Find "Mobile networks"
Tap More....
Step 3 of 6
Find "Mobile networks"
Tap Mobile networks.
Step 4 of 6
Turn mobile data on or off
Tap Mobile data traffic to turn the function on or off.