Problem with Supersonic service

I was with a month-to-month contract with Supersonic for 13 months.

In February 2022 I had cancelled my month-to-month contract with Supersonic and got confirmation via a telephonic call that this cancellation will be effective end of February 2022. A week later, I received a call to return the devices, which I had done via RAM couriers. Subsequently, I received a message of a cancellation fee of R1750 which was deducted. I queried the cancellation fee and was promised to be called, to date no response. On the 3rd May 2022, I was debited for R539 for April 2022 bill. How can this be when I had comp**** with all cancellation rules. I had called the contact center 2 times this morning (4th May 2022) and was kept "on hold" and was cut-off. I need my refunds and the accounts dept to immediately cancel my account.