I get this when I look at the data usage on my s6. It appears under "set data limit". Wish I could post a ss. Any idea how to remove this. It's not on my wife's s6.
I wonder if it's some sneaky adware or tracking app that was installed along with some app you installed. You could try booting into Safe Mode (which disables 3rd party apps) to see if it continues using data: https://support.t-mobile.com/docs/DOC-29226