IOS9 Wi-Fi Assist: There’s a new iPhone feature that’s eating up your data allowance

If you’ve just downloaded Apple's new iOS 9 software, you’ll likely be enjoying a host of new features including better battery life, improved apps and a smarter Siri. But one new feature you may not know about could give you a shock next time your phone bill hits your doormat.

Developers have added a nifty new tool called Wi-Fi Assist in the software update, that’s designed to switch you from wireless networks and onto 4G data when your wi-fi is running infuriatingly slowly.

But in doing so, it might mean the phone is seamlessly switching from your local wi-fi to your data usage without you even realising that it’s happening.

For iPhone users not on an unlimited data contract, this could end up being a rather costly month.

But before you panic and throw your phone into the Thames, don’t worry - because there’s an easy way to turn it off.

How to turn it off

Tap on the settings Settings app and click on Mobile Data (or ‘Cellular’, if you’re in the US).

Scroll down to the Wi-Fi Assist toggle and switch it off - the toggle should appear white, not green, when it's disabled.

It’s as easy as that.

If you’re concerned about how much data you may have used in the past week, the iPhone offers the option of checking up on how much data it has used. In the same Mobile Data settings, you can see “Mobile data usage” for the current period.

Phew. That was close.

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