I have T-Mobile and recently was traveling in WV where apparently there is no coverage. I was shocked to find that I'd used up all my "roaming data allowance" when I had not done anything with the phone the entire 4 hours driving. Apparently various things like my mail were constantly checking in. But I cannot find any way to turn off mobile data! When I'm home my wifi picks up automatically but away from wifi it uses data constantly. My old Samsung s3 mini had a data on/off toggle. I can't find that on the Note 4.