something on my phone is using all my data even though it is connected to WiFi, WiFi assist is off and background refresh. It even happens through the night when I’m sleeping. And today I decided to turn my mobile data off and yet it is still using my data. How?
Verizon says it is user error although I am doing all the things you are doing and yet the data usage is going up exponentially. Apple is supposedly aware of the issue (per an article I read in Forbes) but is unwilling to comment.
Check Settings > Cellular and inspect the details there.
Data usage
