You May Want to Disable Wi-Fi Assist in iOS 9
iPhone owners that have upgraded to iOS 9 might want to turn this new feature off. While handy, it is causing some people to blow through their data plans.
The new setting, which is automatically turned on when a phone is updated to iOS 9, attempts to ensure that users don’t experience any buffering when on a weak WiFi signal. The iPhone will detect when a WiFi signal lacks strength, and switch over to a cellular connection.
