Impossible to cancel an LTE contract

I've been trying to cancel my Telkom LTE contract since 26/10/2017, with no response from the call center or no automated responses. Except for the last attempt on 15/01/2018 which stated that the cancellation's email inbox was full "The recipient's mailbox is full and can't accept new messages at this stage." The only email address I could find was ********** which seems to be useless. Ever since my first cancellation attempt the debit order still goes off every month. I find it ridiculous that a company can grant contracts so easily, and then make it almost impossible for the user to get out of the contract.

Regards, Riaan Smit