Cancellation

I am trying to cancel my contract with mtn & I have been emailing them since the 2nd April however I receive no reply & I have sent like 4-5 emails already but still nothing. I then tried calling the call centre & while waiting in the queue the lines drops then I have to start all from overs & I tried like 8-9 times already I cant do this whole day. Its the 21st April which means I'm probably gona end up paying for another month. I don't mind waiting in the queue but having my call drop all the time is pathetic. I'm not going to pay for another month because of this and I have notice them more than a month in advance.