cellular data

Hi syamryn,

Thanks for posting in Apple Support Communities.

You can view some cell data usage from your iPhone settings, but more in-depth usage will be provided by your wireless carrier.

View how much data you're using 

To see how much cellular data you've used, go to Settings > Cellular or Settings > Mobile Data. If you're using an iPad, you might see Settings > Cellular Data instead.

* Scroll down to find which apps are using cellular data. If you don't want an app to use cellular data, you can turn it off for that app. When cellular data is off, apps will use only Wi-Fi for data.

* To see the cellular data usage for individual System Services, go to Settings > Cellular or Settings > Mobile Data. Then tap System Services, in the list under Cellular Data. Cellular data can't be turned on or off for individual System Services.

* You can view the data-usage statistics for an app from a current period, or view app data statistics for apps that use data when you were roaming. To reset these statistics, go to Settings > Cellular or Settings > Mobile Data, and tap Reset Statistics.

* When you’re using an iPhone with Dual SIM, you can see how much cellular data you’ve used with your selected cellular data number.

To get the most accurate cellular data usage from a current period, contact your carrier.

This text is from the related article you checked out, and should provide the best available information: Use cellular data on your iPhone or iPad - Apple Support

Regards.