Cannot get through to Call Centre

Hi, my number is ***. I have been trying to get through to the MTN call centre since 24 April, but I literally wait for half an hour each time, and still no answer. I have been trying to cancel my contract, and convert to Prepaid. Eventually I went to the MTN Branch last week and filled in the relevant forms. But even the MTN staff told me they don't know when MTN will action my request. This is completely unacceptable!!!