Telkom Refuse to Cancel My Telephone Account!

Telkom refuse to cancel my account. I sent them an email on 5 April 2018 with all the necessary forms and documents to cancel my telephone line. They have yet to provide a response and are charging me each month for the line even though it doesn't exist anymore. I cant even take out a loan because my TransUnion credit score has been impacted negatively for owing them money since May 2018 - money which I dont owe them because they were meant to cancel the phone line.