I'm not using the app, but it says in my battery thingy that it's being used?

I'm using an iphone 6. Then when i checked my battery in settings to see which apps i use the most, my "phone" app is the most used. I DON't EVEN USE THE PHONE APP. Why is it like this?

"Phone" is the radio used used to make and receive phone calls and to send and receive non iMessage texts. It's also used for location based services when a GPS signal isn't available.

The clue is that you are using an i PHONE