@ElsaYou can not Cancel the Wifi, you can close/cancel your internet account, but the Wi-Fi will remain on with the internet connection gone (or until you unplug the wireless access point / router or turn off Wi-Fi on the router)
You can close your account, however there are different ways to do this, ranging from easy to tear your hair out in frustration method.
If you are no longer in the UK, then just stop the payments - assuming that you have been with now for the duration of the minimum term - usually 12 months.
If you want to keep the UK phone number associated with the account you can transfer it to a Voip provider - there will be an onging cost with this, but you will have access to a UK phone number and by transfering it this will automaticaly close the now broadband account
