I want to stop other two sharing network they have connected without my permissi


I have to assume it is a wireless network and you have control of the router.

Simply change the WPA/WPA2 passphrase to something else and cycle the power on the router. Enter the new passphrase into your computer and it will connect. You can also use MAC address permission for an extra level of security if your router supports that. Also change your router user id and password.