You can easily view cellular network data usage in iPhone and iPad (any iOS devices in general). Available data includes total usage and breakdown of your data usage per apps. You can also reset the usage counter if you want to. That's possible with these simple steps;

1. Launch the Settings app by tapping on the Settings icon on the Home screen or by searching for the app in the Spotlight Search.
   
2. Open Mobile Data.
   
3. View general data usage and breakdowns for each applications.
   
4. Scroll all the way down and tap on Reset Statistics.
   
5. Tap on the Reset Statistics option to confirm your action
   
6. Confirm that cellular data usage statistics has been reset.