I am using an iPhone 5s on iOS 10 and nowadays I have been having an issue. I don't have an unlimited Wi-Fi connection as I use my Samsung mobile phone hotspot for my iPhone.
Whenever I connect my iPhone to Wi-Fi, it starts using very high quantities of data, i.e, 2–3 MB every second without any app running. I also tried turning of Background App Refresh and Automatic Downloads are turned off. I tried a soft reset but to no avail. Any idea what's causing this?
Best Answer
Apology:
It has come to my attention 3 years since this original post that my original answer did NOT meet OP's requirements. To the best of my knowledge, there was no easy way to do what OP was requesting in iOS 10. This new answer refers to new settings introduced since this question was asked to provide useful information for anyone else viewing this. Again, my other answer DOES NOT meet the requirements of the question.
NEW ANSWER (works starting on iOS 13):
That's it. For a step by step guide with screenshots, see this link.