How to Fix Increased Mobile Data Usage After Updating to iOS9
After updating to iOS 9, your iPhone will automatically switch between Wi-Fi and cellular networks to provide you with the best possible connection at all times. The downside to this is that your iPhone could end up using a lot more data than you anticipated.
If you’ve noticed your device is gobbling up your allowance for no apparent reason, it’s likely Wi-Fi Assist is to blame. Here’s how you can disable it.
1. Open the Settings app and tap “Mobile Data/Cellular”.
2. Scroll to the bottom of the page and disable “Wi-Fi Assist”.
It’s that easy! With Wi-Fi Assist turned off, your iPhone will no longer switch to a 3G or 4G network automatically when your Wi-Fi connection is spotty, which should prevent unexpected data usage.