A few days ago my iPad Air 2 registered a usage jump from 4.5 GB to 10 GB. I talked to a customer support person and they said there was some sort of mistake and fixed the issue. Yesterday, the problem happened again and the customer support person said I used 5GB in a 260 minute session and you're SOL. My wife uses her iPad for Facebook, email, and browsing. She did not watch any videos - not that I don't trust my wife, but we don't get enough bandwidth for streaming - it takes several seconds to even render the home page for google searches - so I'm really sure she didn't use up bandwidth on videos. Our system services including hotspot register less than 300 MB of usage this period so far, so it is not a background task - unless there are mystery unmonitored tasks going in iOS. This unexplained usage spike stuff doesn't work for me because I need a reliable system, also note (if it is a helpful clue) that my system says I've got 14.9 GB of usage on a 10 GB plan. While I'm annoyed that I basically lost 1/2 of my 80 dollar plan I am very, very grateful for pay as you go.