I’m always the first to tell people to update their technology devices whenever the manufacturer releases a new update. In many cases the updates include new security fixes as well as new “features” available for the device.
If you’ve noticed that your data usage has skyrocketed since installing iOS 9 then this may be caused by a new feature on your iPhone called Wi-Fi assist. For some of us, Wi-Fi Assist may be more of a bug rather than a feature.
Wi-Fi Assist automatically switches your iPhone to use your cellular data plan if you happen to be in a spot where Wi-Fi coverage is poor. This sounds great in theory, but if you’re not on an unlimited data plan then all this extra access on your metered data plan could result in a nasty shock when you get your next bill.
Compensating for poor Wi-Fi when you’re out and about is one thing, but with this setting you could be burning through your data allowance when sitting at home or in your office.
You can find the switch to turn off this feature under Settings > Cellular and then scroll to the bottom of the (very long) page till you see the Wi-Fi assist entry
Note that the default for this “feature” is on.
This could be a useful feature, and it’s a shame that the toggle for it is buried at the bottom on an obscure page under Settings that most people will never venture into, because it’s one of those things that would be nice to be able to turn on if the need arose.
You can keep an eye on your usage by periodically using the Reset Statistics feature, which you can find just below the Wi-Fi Assist toggle detailed above. I do this on a regular basis since I subscribe to a limited data plan that’s shared with other users. If you’re on a limited plan then doing this monthly could help you keep an eye on your data usage as well.
A few days ago Apple released the iOS 9.0.2 update to fix this and a number of other issues – If you’ve already upgraded to iOS 9 then it’s time to install the latest patch or at the very least, change the Wi-Fi Assist settings before your next billing period rolls around.