Contract cancellation

Knowing my contract expires in June 2019, I visited the MTN shop in Brits Mall. They told me to phone 135 about 2 weeks before expiry date. I called 135 and selected the option for contract cancellations. The agent did a security check, I said I want to cancel my contract and put my number on prepaid. The agent confirmed my last payment to be in June 2019 and provided me with reference number ***. July debit order deducted and I reversed at my bank. August the debit order deducted double and I reversed it again at my bank. I visited MTN in Brits Mall once more. There they come up with a story of a client giving notice first and then having to call again to confirm cancellation. This was the first time I hear about that. On Monday 02 September 2019 I call 135 once more and select the contract cancellation option. Hadisele do security check and confirms that no request for cancellkation was done. She says that she will do a request to listen to the recording and let me know within 48 hours giving me reference number ***. I called 135 again on Wednesday 04 September 2019. She is unavailable and another agent asks her about the case. Apparently the recording cannot be traced, the only information is notes made on the system saying customer called in to cancel contract and call was transferred to retentions department. Thereafter nothing. Now my services are suspended and I am threatened with laywers. Isn't it convenient that the recording now diappeared? Being a loyal customer of MTN for 6 years and now I will decide to stop paying? If the notes mention customer call to cancel contract, what would the rest of the conversation consist of? I am very diappointed.