The only thing I've found with Consumer Cellular is my data miraculously goes up, even when I don't use my phone. My wife uses hers more, (surf's on Google, etc.), and by the end of the month, both of our data is near the maximum. (The little bar goes from green to yellow, then finally to red when it's close to max.). I think it tries to get you to go over so they can sell you a bigger plan.
The only thing I'll use data for on the phone once and a while, is to remote start my new Jeep with a App. I put in from Chrysler. Even that uses very little. It a racket. I'm going to try leaving the phone off, turning it on just to use it to make a call, and see what happens. Probably the same thing.