Why does my phone say I'm using data for apps when I don't ever use data?

[Pkerry]

The phone in question is a prepaid phone with a talk and text plan only. I only use wifi. I don't have a data plan. Nothing that requires a connection works on this phone without a connection to Wi-Fi.
However, In settings- connections-data usage-it says that Chrome has used a bunch of data this month, I think YouTube has and other apps. It has a graph showing all the data I've used. I'm puzzled, does this make sense?

 

[methodman89]

The phone os will use data in the background, even with Data turned off. How much data was used?

 

[B. Diddy]

Welcome to Android Central! Are you sure you're looking at the Data Usage screen for mobile data, or is it for wi-fi?