Upgrade cancelled but account still debited

I'm disappointed and very angry with MTN and the saddest part is I've sent emails to their Retentions, their Complaints and Credit department to which no one cared to reply or acknowledge. In March I did an early upgrade, to which I was advised if I change my mind I can cancel or change so long it's within 10days of receiving new device. 2days after receiving device,I returned it. I called Retentions to confirm they received the device. I then requested a cancelation of which they didn't process, so I was invoiced R3300 for upgrade. I queried with them and I was told they will Credit my account and cancel. 3months later non was done. I called again on 24thMay and I got ref: *** to which the lady told me they will cancel my contract ***) and credit the MTN account in 7days. Today 9thJune I call to find out when my second contract ***)ends,and I was advised that the R3300 for the contract that's supposed to be canceled has been carried over to the second contract. I've been waiting for over 2months for this upgrade to be canceled and my account to be credited but no one is resolving it. Now my name has been affected as the account is handed over