My iPhone 📱 6 turns wifi on Automatically even after switching off wifi after some time without any actions from use,Below is attached screen shot of before sleep and after sleep

When you toggle the Wi-Fi button in Control Center in iOS 11, it only disconnects but does not turn off. It will automatically connect again in the following situations:

• You turn on Wi-Fi in Control Center.
• You connect to a Wi-Fi network in Settings > Wi-Fi.
• You walk or drive to a new location.
• It's 5 AM local time.
• You restart your device.

Use Bluetooth and Wi-Fi in Control Center with iOS 11 - Apple Support

My iPhone 6 does the same thing. I don't like it. If I turn it off it should stay off. If I turn it on it should stay on. To me, this is a way to track location without your consent. Its BS and my next phone will not be an iPhone. Latest update has been full of problems. I'm hating Apple products more than ever.