Is it rocket science to cancel a contract

I took out a Telkom contract with Mondo in December 2019 however I canceled it within the cool off period. I got a call from Mondo to confirm that the contract has been canceled and the reference number is as follows 40026 but to my surprise I received a statement from Telkom reflecting the canceled contract amount. I phone Mondo on the 17 January 2020 and they told me that the contract was not canceled and I requested that they cancel it but it was never done. I have been calling Mondo (24,27, 28 January 2020 and 21 February 2020) ever since with no luck, all I get is excuses. Can Mondo please cancel the contract and refund me my money.