I am having this issue but only on one line. My son's phone is showing data usage constantly. It is charging it as web data, but he has his cellular data turned off for Safari. This has been happening the last couple months after we had to have his phone replaced with a refurbished iPhone 6S. Could that be the issue? I had him go through and turn off data to all is social, web, and game apps. He is still showing data usage that jumps a full gig every couple of days. He looks at his data usage on his settings though and it shows he has barely used a single gig since his data reset. What is happening? We also turned off his location services, and it still shows that data is being used every couple of minutes. He is currently on a trip with his grandmother but when he returns we are going to a Verizon store to get this straightened out.