Check iPhone's Wi-Fi settings to prevent runaway data use

What sinister new feature in Apple's iOS 9 could be costing you money?

I almost feel like I'm writing one of those click-bait headlines on Facebook designed just to get you to click on the link.

There was a lot of press coverage recently about a new feature in the iPhone's latest operating system called Wi-Fi Assist.

Simply put, there are some times when your iPhone is connected to a Wi-Fi network, but because of your location or poor Wi-Fi signal strength, your Internet connectivity grinds to a halt.

Until last week, if your iPhone was in Wi-Fi purgatory, you'd just have to wait it out or bring up the settings and turn off Wi-Fi so your cellular connection could finish the job.

Apple realized Wi-Fi purgatory was a problem, so it introduced the Wi-Fi Assist feature that lets the iPhone realize the Wi-Fi signal isn't working and make the switch to use cellular data all by itself.

Great! Problem solved, right?

Yes, the slow Internet problem is solved, but what you might not realize is even though the phone's status icon shows you're connected to Wi-Fi, you might be eating up your iPhone's monthly data allotment.

For many people, going over the monthly data cap will cost money.

I know many parents who have their families on plans with fixed amounts of data because they know when their kids are home, any cellphone data use is over the Wi-Fi.

Little Suzy could be in her room, happily watching Netflix on her iPhone over Wi-Fi, but if the phone decides to use cellular data instead, you could be talking serious data overcharges.

Apple has turned on Wi-Fi Assist by default in iOS 9.

To turn off Wi-Fi Assist, open your iPhone's settings app and choose Cellular and scroll all the way to the bottom.

Not everyone will see Wi-Fi Assist in their preferences, as older iPhones (like the iPhone 4S) don't have the option, so if you don't see it at the bottom of the Cellular preferences, you don't have to worry.

Everyone's situation is different, so it pays to know where the setting is and what it does.