Failure to stop a contract for more than a year!!!

I received a phone call on the 9th of Oct 2020 to upgrade my phone to a Huawei P40 and a ****le. I received both on the 15th and on the 17th I returned said phone to MTN Centurion (thus within the 10 day return period) and received the cancellation sms on the 19th. In Nov and Dec 2020 I was billed for all my accounts includung the one I cancelled. In Jan my debit order bounced... I did not have said amount because I did not have the cancelled amount included.

After various complaint in Jan, Feb and Mar 2021. They then stopped. After upgrading again with my ling standing contract they again started deducting the cancelled amount.

I am furious that more than a year later I have been paying for this phone. The amount over this time uas accumulated to R 5 508-00 give or take. This is unacceptable. I am fed up and I'm considering cancelling all my contracts with MTN with whom I have been a client for, for more than 13 year!