A feature of Apple's new operating system may unknowingly lead to huge phone bills.
What iOS 9 also comes with, however, is a default setting known as WiFi Assist.
The setting automatically uses cellular data instead of WiFi when the user is in the presence of only slow WiFi networks. So even though WiFi Assist will result in a faster Internet connection, it will likely use up large chunks of data in the process, adding extra fees for users without unlimited data plans.
Thankfully, the new feature is easy to turn off.
Simply open up settings, tap "Cellular" and then scroll down to find "Wi-Fi Assist" at the bottom of the page. Toggle the setting off by turning the switch from green to white.
To check the amount of data your phone used, go again to settings, tap "Cellular" and scroll down to find "Cellular Data Usage."
Accessing this section will provide an estimate of how much data your phone used since the data counter was reset, according to The Washington Post.
But for those who never accessed this screen before, the counter has likely never been reset. Such users should go back to the "Cellular" menu and tap "Reset Statistics."
The data counter will not reset on its own, so it's recommended to manually do this every month.