Impossible to cancel the MTN contract

Yesterday, I've called to cancel my MTN contract and it was said that I would have to go to a store to pay for the cancelation fees. I've been to the store, I've paid the value that it was said to me via phone and my problems started. Today, I'm trying to do the cancellation and I'm facing the following problems: 1 - The call center cannot see the value paid yesterday; 2 - The call center is telling me now that I've paid the wrong value, even though the value was given to me via MTN call center; 3 - Nobody can tell me what would be the difference to be paid; 4 - All the time that I call, all the above happens and the call mysteriously ends.

I really need help to have my contract cancelled because I'm leaving SA.