Data backup every three hours, even when connected to wifi

It's more than likely your carrier transferring your usage statistics at that time. It's not really using all that much, correct?

You may want to call your carrier and check with them to see if that is what this was.

That is pretty unusual. You can try turning off data access to both of those apps in settings if that is a concern. Not sure why they're doing that while you're on wi-fi, however...do you have wi-fi assist turned on? That's under Settings > Cellular all the way at the bottom. Some folks have been reporting that it's using up data unnecessarily.

ridod wrote:

My phone has been in my office and connected to wifi since this morning so I figured I'd reset my data statistics to see what's up. Turns out it's Siri and "exchange accounts" using data, even though I NEVER use Siri (and of course I've been connected to wifi).

Any thoughts?

Let's explore "connected to WiFi." Any iPhone is connected to WiFi under only 2 conditions:

1. The screen is on and in use; that is, the phone is not asleep - or -
2. The phone is connected to power.

That's it. If the phone is asleep and not connected to power WiFi is turned off to preserve battery life.

In addition, Exchange accounts, iCloud accounts, Hotmail, Yahoo, Gmail, etc use Apple's Push service, which only works over cellular data. If WiFi is on only the notification will go via Cellular, and actual message downloads will use WiFi. But only if WiFi is on as described above. This is true for other features also; Visual Voicemail always goes over Cellular data. As do Notifications.

Finally, on your 3 hour observation, your carrier's switches report cumulative usage to the billing system every 3 hours. So that number is not data that was used at the 3 hour timestamp, it is data that was used at any time during a previous time period. It doesn't even have to be in the past 3 hours; it can be data older than 3 hours, because each switch reports to the billing system on its own schedule.