Samsung S6 using data that's switched off

[Jazzie1111]

I only use my phone through Wi-Fi and always keep the mobile data off yet my data is going down. My allowance only renewed yesterday yet data has been used already! Why?

 

[B. Diddy]

Are you looking at your carrier's accounting of how much mobile data you've used, or the phone's accounting? They don't always match up. For example, MMS (picture texts) require mobile data, but they don't count against your carrier's monthly allowance.