How can I tell what my data is being used for in iPhone

To see how much cellular data you've used, go to Settings > Cellular, then do any of the following: See cellular data usage for individual apps: Scroll down to your list of apps, then tap Show All. The amount of cellular data used appears below each app.

View or change cellular data settings on iPhone - Apple Support

SIMcdiphone14 wrote:

How can I tell what my data is being used for?

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