What must one do to cancel a service!!!!

Please assist urgently with cancelation of ADSL line, TIN ***.

This is under my dad's name. He went into your branch on Saturday and they could not assist so someone called him and the lone was not clear and they never called back. In addition, he is trying all the numbers available online but is getting no joy.

I have tried to do it online however the OTP is not sent to my dad's number for us to proceed. I cannot cancel using the online services as we don't get the OTP.

This is highly frustrating and such a mission just to cancel a service.