IPhone 6s plus DATA

[FitzyChick]

Since buying my son the IPhone 6s Plus a few months ago,  our Data usage has tripled and then some.   We've had to increase our Data from 10GB's per month up to 20 then to 40 and we are still going over.   Only on his phone do we  have an issue.   The other 2 phones are Samsungs and use a normal amount of data.   The iPhone,  literally,  bleeds data.   Even at home,  while connected to a very strong Wi-Fi,  his uses data.   I've corrected iCloud issues... No help.... I've turned off data usage for Every app individually,  and then the main cellular data button off.... Still used 3 GB's in 1 day with all of the above turned off!!    This is the 3rd or 4th month that we are almost at $100  in overage costs and our month in not over for another week!    I'm at a loss and just don't know what to do!    HELP...... PLEASE!

[pherson]

That is entirely impossible. He is going right back in the phone turning them back on and then when you ask for the phone they have been turned off again....by him.