Contract cancellation is simply impossible

MTN, how is it possible for me to open a contract in the store but i cannot cancel at the same store? And your call centre in non-existence. Nobody pick-up the phone. Been trying to call since monday trying to cancel a contract but no answer after 30 minutes of calling. But when it comes to upgrades, you are very quick to pick-up the phone. Thats bad customer experience i do not want to experience again.