data usage when data is turned off?

[BENTLEYBLVD]

Purchased 11 yr old a iphone 5 for Christmas.  I set it up and all data is turned off.  She can use it to chat with friends when home on wifi and she loves to facetime with them.  Again, on wifi with data turned off.  She used 5 GB last month, how???  I have gone through the entire phone and nothing is turned on for cellular, just using wifi at home.  Outside of the home she just uses it to call or text me.  help?

[SuzyQ]

Check the apps list - there will be toggles for using background data on cellular for updates and such.  Turn them all off.

Turn OFF wifi assist if it is on - it will switch to cellular if it feels wifi isn't strong enough.

What does the phone say is using the data?  iPhones will give you categories, not specific apps - Video, social, email?