I know this is an android forum but......

[Thatdad]

You may want to have a look at the iMessaging or whatever the group messaging is called. My 19 yr old usually sends / recieves ~5000 SMS messages a month. On iPhone when you use the group messaging it doesn't send as SMS, but uses data.

Group and just iMessages themselves.

Seriously all they do is show is that it sent, and that someone received it.
If memory serves me correctly, it uses about 1-5kb per sending and person viewing it.

That would add up to around 25000 kb if he was to send 5000 like your 19 year old does.

Facetime over 3g is about 15 mb per 10 minutes.

An hour of facetime over 3g/4g is 90 mb. Sorry did my math wrong. It's early here.

That's the simple stuff. We haven't touched base on apps, syncing (which still happens even if you shut off apps through the home button by the way) app updates (sometimes as much as 1-100 mb. Depends on the app. Oh and push notifications.

 

[SammanthaX345]

Do you know if iCloud is turned on? If it is you need to turn most not if all off. Also have him turn off cellular data when he's not using the device or using on WiFi. This will help when WiFi disconnects and he doesn't realize right away.