Theft by MTN

My experience with MTN is terrible. I took out a cellphone contract with MTN, (number: ***) on 5 September 2020. I subsequently returned the phone on 8 September, because I was not happy with the contract. I called MTN to cancel the contract and immediately sent an email on 7 September. MTN collected the phone at my residence on 8 September, through DSV with Parcel ID M777WR136A***BCC3. The returned phone acknowledged by MTN on 11 September and no damages were identified and the phone was deemed to be in good working condition. MTN has a cooling off period of 5 working days where one is allowed to return the products without incurring any penalties. I returned the phone within the colling off period. However, MTN persistently charges me a cancelation fee of over R 6000, which they are not supposed to because I returned the phone within the cooling off period with the phone still in its original condition, and MTN acknowledged this. I have called more than 5 times to inquire about this issue. The reference numbers are (a) *** 11, (b) ***(c) *** (d) 296 151 387. The last communication with MTN was on the 11th November with Themba, (reference number: 296 151 387. Themba promised to inquire and call me back about my issue. Since then he has not called me back. Prior to Themba, I had a call with Nodoli Mazibuko, (reference number: ***), she notified me that the MTN just automatically charges you the penalty fee regardless of whether you canceled on time, however, she promised to escalate the matter so that the issue is resolved. I have to call my bank every month to reverse the debit order dekm MTN, who I do not have a contract with. They keep changing their reference number in order to debit my account. MTN is a *****. They would rather keep changing their reference number to debit my account wrongfully than to resolve my issue. That is so disgusting.