iOS 9 upgrade
I recently upgraded my iPhone6 to ios9 and ran into a couple of issues that really jacked my data rate usage. I have a 6gb plan a noticed that the App Store was using a ton of data and that I had used some 4.5gb of my data about 20 days in. The culprits were the App Store app allowed to use cellular data, and wifi assist which overrode bad wifi connection with cellular data. Both contributed to larger than normal data used. I normally run around 2-2.5gb due to wifi everywhere.