iOS 9 'Wi-Fi Assist' Could Lead To Huge Data Bills
Turn off WiFi Assist, save your Data Usage
One of the new features introduced in iOS9 is "Wi-Fi Assist." This enables your phone to automatically switch from Wi-Fi to a cellular connection when the Wi-Fi signal is poor. That's helpful if you're in the middle of watching a video or some other task on the internet that you don't want interrupted by spotty Wi-Fi service. Unfortunately, Wi-Fi Assist is enabled by default, which means that users may exceed their data cap without knowing it because their phone is silently switching their data connection from Wi-Fi to cellular.
Turn off Wi-fi assist now.
It's located at: Settings -> Mobile Data -> W-Fi Assist (all the way at the bottom). Yes, it is turned on by default.
Cheers
Rescue PC