http://www.techradar.com/news/ios-11-control-center-wont-actually-turn-off-bluetooth-or-wi-fi

iOS 11 brings with it a significantly revamped Control Center, and love it or hate it, there's a bit of a 'gotcha' when it comes to Bluetooth and Wi-Fi. 

Turns out that turning off either one in the Control Center doesn't actually toggle them off. You'll need to go to the Settings to disconnect Bluetooth and Wi-Fi completely.