SHOCKING LACK OF SERVICE FROM MTN!

Upgrade reminder sms received. Rep**** 'yes' and got a call back to initiate upgrade. Received new product (Huawei PSmart 2021). I was not happy. 24 May 2021- I returned product & accessories to MTN, Fourways Mall for cancelation, as instructed by the service centre, ref ***. I have spent HOURS on calls to NUMEROUS service agents since. NOBODY can help me with an upgrade cancelation?! I'm told a 3rd party did the upgrade, this is not my problem, MTN surely needs to assist! The last 2 refs I received: *** & ***. Almost a month has passed. Can someone HELP?! I am absolutely shocked at the incompetence!