In NM options, choose "Edit wireless networks" and remove one of the previously connected wireless networks. Verify that it was removed.
- click on the network connection icon on the notification area
- Click WiFi section
- click WiFi settings
- Click History -> Select the one connection which is in used from the list-> Click Forget
- Click on Forget to remove all details relating to this network
vp5. the wireless connection can be removed successfully. And the Wi-Fi status will show "Connection disappeared"