I have an iPhone 8 with 2gigs shared data with 3 other phones (iPhone 5 and 2 iPhone 6's). Our data drains like crazy even though we rarely are using the data network. All phones have apps turned off to data network - heck the other phones don't even have social media apps to use data! I'll even have the data switch turned off and the data still drains. When I open up the data utilization it shows 41% web and 33% social media - both of which I only use if I'm connected to wifi? Is it possible for people to "steal" your data somehow? This issue has perplexed me for years!