In iOS 11 and later, when you toggle the Wi-Fi or Bluetooth buttons in Control Center, your device will immediately disconnect from Wi-Fi and Bluetooth accessories. However, both Wi-Fi and Bluetooth will continue to be available, so you can use:
● Apple Pencil
● Apple Watch
● Continuity features, like Handoff and Instant Hotspot
● Instant Hotspot
● Location Services
This differs from all other versions of iOS where toggling Wi-Fi or Bluetooth in Control Center would turn them off.
Instead, what actually happens in iOS 11 when you toggle your quick settings to “off” is that the phone will disconnect from Wi-Fi networks and some devices, but remain on for Apple services. Location Services is still enabled, Apple devices (like Apple Watch and Pencil) stay connected, and services such as Handoff and Instant Hotspot stay on. Apple’s UI fails to even attempt to communicate these exceptions to its users. It gets even worse. When you toggle these settings in the Control Center to what is best described as"off-ish," they don’t stay that way. The Wi-Fi will turn back full-on if you drive or walk to a new location. And both Wi-Fi and Bluetooth will turn back on at 5:00 AM. This is not clearly explained to users, nor left to them to choose, which makes security-aware users vulnerable as well.
If you want to completely disable Wi-Fi and Bluetooth for all networks and devices, follow these steps:
● To turn off Wi-Fi, go to Settings > Wi-Fi and turn off Wi-Fi.
● To turn off Bluetooth, go to Settings > Bluetooth and turn off Bluetooth.
Hit the link below for the EFF's full post on the matter...