Mysterious data usage in System Services

I am averaging about 15 MB of usage a day and I can't figure out what I am doing. According to Settings>Cellular, my app that is the biggest user averages about 1 MB a day. Most of my apps are turned off as far as cellular data is concerned. Then there is System Services which uses about 7 MB a day. The worst offender is Exchange Accounts followed by iTunes Account, General and Siri. I don't even use Siri! Rarely do I start iTunes and what are Exchange Accounts and General? Any illumination will help.

iPhone 5

iOS 9.0.2