Cellular data usage

Greetings Cellulardatausage, 

It would be helpful to know what indicators you’re seeing to show the cellular data usage. That may help shed some light on the situation. 

Next, be sure that Wi-Fi Assist is disabled. Go to Settings > Cellular or Settings > Mobile Data. Then scroll down and tap the slider for Wi-Fi Assist. You can learn more about this feature and how I uses cellular data in the following article - About Wi-Fi Assist. 

Then if you use an Exchange ActiveSync account, it might continue to use cellular data even if you turn Cellular Data off for Mail and Calendar. To see the cellular data usage of your Exchange ActiveSync account, go to Settings > Cellular > System Services.

Thanks. 

Some types of data cannot use Wi-Fi. Specifically, Notifications, Visual Voicemail, and SMS/MMS messaging to non-iPhones.

iPhones will not use cellular data for iOS updates unless it is a model that supports 5G, and your XR does not. You can choose whether to update apps using cellular data in Settings/App Store.

If you turn off Cellular Roaming it will not use any cellular data or voice when you are not connected to your registered network, essentially while traveling outside of your home country.