Disconnecting nearby Wi-Fi until tomorrow ?
iPhone 7, iOS 11.2.1, And IPad Air 2
Did you click the Wi-Fii button in the control centre screen behind that message?
The behaviour of the Wi-Fi button is to disconect from whatever Wi-Fi you are on until you reconnect by pressing the button again, or until the next day.
See this article for details Use Bluetooth and Wi-Fi in Control Center with iOS 11 - Apple Support
Disconnecting nearby Wi-Fi until tomorrow ?