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?