Billed for telkom's error

I previously opened a contract for my cellphone and Telkom erroneously opened two contracts on the same phone. After a long and painful cancellation process for their error (case: ***8), I was charged this month for the cancellation of their mistake! How does that make sense to charge for cancellation of the contract that they mistakenly opened. I have lost all hope with telkom mobile and will be moving to another company once the contract period is over. All that I need help with now is obtaining a refund for the cancellation amount.