If you've upgraded to iOS 9 or bought a new iPhone 6s or 6s Plus, a new setting could be eating up your monthly cellular data allotment while you thought you were using your local coffee shop's Wi-Fi. Apple calls the feature Wi-Fi Assist, and it's meant to help you out when you're on a wireless network that's too crowded (or too far away) by dipping into your data to keep you connected.
While the feature is meant to aid users, Apple doesn't appear to program caps or limits into it. Unless your cellular provider sends you alerts based on your usage, you could get hit with a ton of overages just because a network you trusted wasn't performing to Apple's standards. The implementation of this potentially useful feature seems a bit short sighted, but thankfully it's not difficult to disable it.
MORE: Apple iOS 9 Review
How To Disable iOS 9's Wi-Fi Assist
1. In the Settings app, select Cellular.
2. Scroll to the bottom of the menu and turn Wi-Fi Assist off.
Now only you can be blamed for eating up your data allotment!