Can't cancel my contract

I have a 10GB wifi contract with Telkom and my 24 month contract ended Dec 2017. As per Telkom's requirement I sent in a cancellation form 21 working days before the end of Dec so that I can have my contract cancelled. I have been struggling since 16 NOVEMBER 2017 to cancel this contract! I sent in my form to a department that has no number, you can only reach them by email but they never send anything back. I phoned their call centre 5 times in November to December to ask what is going on. I called them in Jan 2018 because there was new data loaded onto the wifi contract and they said they don't know & I need to call them again. The second call in Jan 2018 the lady said she escalated my enquiry, I sent an email to the cancellations department again and I sent an email to their complaints department, I have not received one call back. I'm so sick and tired of struggling like this! Why is it so difficult to cancel a contract!!