SOLUTION! (NO NEED TO RESET YOUR IPHONE SETTING!)
I have the same issue for the last two weeks. But i have already managed to solve the issue all by myself. When i go to Settings > Cellular > below the tab "use cellular data for:", i turned off some apps which i didnt want to use with cellular data. As soon as i go back to Settings, and then i went back to Cellular, the apps which i had switched off earlier, automatically turned back on.
Here's the solution:
Either you're using wifi or cellular data, first of all you're gonna hafto turn on the cellular data use for App Store. Once you have turned it on, go to App Store application. Update ALL the apps which have new updates available. If it asks you to log in your App Store, just do so. If there's something wrong with your debit or credit card information, it will ask you to update to a different card. Just do what it asks. Put in a new credit or debit card info and fill in the forms provided. The card you're using must be usable and has usable balance in it. Let's say atleast $10 to $20. As soon as it confirms your card successfully, the app updates will start automatically. Continue to update all the apps. After all updates are finished, go back to Settings > Cellular. Try to switch on or off some apps for data use and recheck.
Try it yourself! Have a nice day and don't put a blame on Apple for this.
From Malaysia, with love.