No response from MTN on any channel

Trying to cancel my contract with MTN (ironically due to poor service delivery). Last week I phoned the call centre twice and held for 20-30 minutes before giving up. I then sent an email per their website (which advises that a response will be received in 3-5 working days). No response or acknowledgement a week later. Called a store over the weekend and they told me the call centre has to assist. First call this morning I held for 40 minutes and then got cut off. Am now on my second call for the day (20 minutes and running). Cannot cancel my contract because I can't reach them! It would be funny if it wasn't infuriating.