How Do I Stop Certain Apps From Using Cellular Data On My iPhone?
Open the Settings app on your iPhone and tap on Cellular. Swipe down to the section called "Cellular Data". It may take a while to load as the iPhone gathers cellular usage for each app. You will see a list of apps and also information about how much cellular data each app has used. Toggle the button next to each app name to stop it from using Cellular Data. If you have accidentally used more data than anticipated, the problematic app can usually be pinpointed on this screen.