If you're on a limited data contract and you've updated your iPhone to iOS 9 you may be in for a bit of a shock when the bill comes in. The new software update puts Wi-Fi Assist on without a notification, so you may have been using extra mobile internet without knowing it.
Wi-Fi Assist is a feature that proves pretty handy and when your Wi-Fi network connection is failing it will bring in some of your mobile signal to make sure you're not lagging behind.
But if you've got limited data on your contract it means you'll be eating into that amount, and may be charged a little extra by your provider. It's also a bit cheeky that iOS 9 doesn't notify you that the feature is switched on.
If you don't have unlimited internet or a large data package you should head into your Settings app to switch off Wi-Fi Assist.
You'll find it under Mobile Data and at the bottom of that menu you'll find a toggle to quickly switch it off.
If you're lucky enough to have unlimited mobile data then it's worth keeping on as it's a really useful feature that will give you much better internet than when it's off, especially if Wi-Fi is patchy around your home.