Paying for a service that's been cancelled months ago

I've cancelled my service with Telkom via e-mail end of May 2017 . The service was cut off shortly after that ... I noticed a month later that they still billing and deducting the money from my account , i phoned and was told to mail them again . About Six weeks ago i actually went to a Telkom store at Festival mall in Kempton Park and cancelled it over the counter where i was promised that it will be processed with immediate affect and a refund would be done for the other months as she picked up that i've been paying all along . Guess what i'm still paying . i'm fed up with them and will never ever use them again