MTN refusing to cancel contract by ignoring my requests

MTN is refusing to cancel my month-to-month SIM card only contract.

I have sent several emails requesting this over the past few weeks and have been ignored by MTN. Today I phoned MTN retentions 3 times and spoke to an agent named Precious. The first call she told me her system was slow so she was putting me through to another agent. After waiting for 10 minutes to be put through the phone was answered and I could hear the noises of the call centre in the background but nobody answered. I phoned back again and was put through to Precious again. She put me on silent for 10 minutes and didn't answer when I kept saying hello. The third time I asked to speak to a manager and was told that the managers were busy and unavailable and she wouldn't put me through to a manager.

MTN is not above the law and blatant disregard and ignoring requests for cancellation are unacceptable and *******.