Apple’s settings for controlling use of cellular data are a weird mess.
A mess because they’re scattered over many screens, and weird because one of those screens (“Cellular Settings”) starts out empty and only gets entries as various apps try to use cellular data.
Here are some screens to look at and a few changes to be sure to make if you want to control your data use (Tip: The fastest way to get to these screens is to ask Siri to take you there. For example: “Show my settings for Podcast”.
Podcast app: turn off use cellular data
(Not everyone has this Apple app installed. If you don’t see it in settings don’t worry.)
iTunes and App Store: Turn off use Cellular Data
IN Settings tap on “Settings” then look at VIDEO and set Auto-play to Wi-fi only (or off)
Background App Refresh
Siri might not find this one. Tap on Settings General and its in there.
Turn off most of these unless you REALLY want it running in the background. Few things need to do that.
This is the weird one that only shows an app AFTER it’s accessed cellular data. It also shows data used (I tapped the reset link on this page TWICE recently, so most aren’t showing anything.)
It’s weird, but it’s the most important of the bunch. Some of my big offenders are Photos, Videos, YouTube, Podcasts, iTunes Store, Hangouts, FaceTime, Evernote, Dropbox, Google Drive, Camera+, and App Store. I turn them all off for both Emily and I.
To configure this on a new phone you need to turn off WiFi, connect via cellular network, then launch every app on your phone. Then you’ll see a complete list you can edit. Every time you add a new app to your phone you have to repeat this. Yes, this is a terrible user experience.
PS. You can lock Cellular Settings in Restrictions — handy for kids on, say, Ptel. Other settings, like App Store cellular data use, can’t be locked.