Apple's 'WiFi Assist' Feature Could Cause Surprising Spike in Data Use

Keeping track of your data usage isn't always an easy thing to do. And now several iOS 9 users are questioning whether a feature in Apple's new operating system designed to keep your connection stable is a potential data sink in disguise. The setting, called "WiFi Assist," automatically switches your phone over to the cellular network when you're in a place with spotty Wi-Fi.

The feature is on by default in iOS 9, meaning that your iPhones and iPads will seek out cell networks unless you tell them not to -- and could potentially eat up your data plan without you realizing it. It seems as though the problems start when users think they're somewhere with a good Wi-Fi connection, but their phones beg to differ -- leading to bill shock. Users concerned about that can turn the feature off near the bottom of the "Cellular" section of their Settings app.