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.
Step 1 of 5
Find "Mobile Data"
Tap Settings.
Step 2 of 5
Find "Mobile Data"
Tap Mobile Data.
Step 3 of 5
Turn mobile data on or off
Tap the indicator next to "Mobile Data" to turn the function on or off.
Step 4 of 5
Turn use of mobile data for applications on or off
Tap the indicator next to the required application to turn the function on or off.