Why is my iphone using so much data?

I have the iphone 5s. I make sure all the time to keep my internet offline. If I ever use internet (which I don't) I use my house's Wi-Fi. I don't know why it keeps loading up on my data. I don't have an icloud account, I made sure to delete my emai from the phone… What else could it be? The only thing I did yesterday was look at my Verizon account to see how much data has been used. And I played the offline version of candy crush the game. What could it be?

Added (1). I forgot to mention, my phone is connected with my siblings internet plan (Wi-Fi)… Could that be the reason too?

Added (2). @Aleks-Yes that's what I meant, lol

I'd call Verizon and ask them they should be able to tell you what's using your data.

What do you mean by "keep my internet offline"? There's a setting to have it use internet only on Wi-Fi. When it's on your usage of 3g/4g should be 0.

Sounds like your "sibling" is using all the shared data if that is what your saying.

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