Telkom/Mondo *****ing money from people

I had a sim contract with Telkom or Mondo last 2019 October,so the sim card was not working and when I contacted them they told me the sim card will not work because they do not have network coverage where I stay,I asked if there were any alternatives and they said there were none,so I asked them to cancel the contract on the 26th of October,they said they would cancel the contract but to my surprise they deducted money from my bank account anyway,O contacted them and made an enquiry with that and they told me they were still in the process of cancelling the contract and I should wait for 7 days,they even said they would contact me when the contract was cancelled but they never did,instead they are still deducting my money and today they deducted 998.This is just ***** because you can't make people pay for a service they are not using