You can adjust the settings in your phone or tablet to use less data.
Switch off automatic updates to update only when you’re on WiFi
If you’re using too much data, switch off automatic updates.
Apple device – go to Settings, then General, then Background App Refresh. Then turn it off. You can still choose to keep it on for certain apps.
Android device – do this on an app-by-app basis. It doesn’t stop your apps refreshing when connected to WiFi. Go to Settings, then Data usage. You can see all the apps using data. Choose an app, then Restrict background data.
Use WiFi when you can
Make use of available WiFi networks and WiFi hotspots when you're out. WiFi Assist on iPhone can use data if it's constantly looking for WiFi networks. So you may want to switch it off and manually connect when you need to.
For auto back-up services like Dropbox or iCloud, choose the WiFi only option.
Switch it off if you don’t need it
Cut down how much you tether your phone or use it as a hotspot.
Turn off features when you don’t need them, like Location.
Turn off mobile data when you’re not using your phone, such as when you’re sleeping.
Other handy hints
Make use of available WiFi networks and WiFi hotspots when you're out and about. It's worth mentioning that WiFi Assist on iPhone can actually use up more data than you'd expect if it's constantly looking for, connecting to, and then disconnecting from WiFi. So you may want to switch it off and just manually connect to WiFi when you need it
For auto back-up services like Dropbox or iCloud, choose the WiFi only option
Limit how often you tether your phone or use it as a hotspot
Turn off features like Location unless you need to use them, to avoid using data
Switch mobile data off altogether when your phone isn't in active use – for example, if you leave it on overnight for your wake-up alarm.