UNAUTHORISED DEBIT ORDER

I upgraded my DSTV decoder with them on a 2 year contract. I paid the contract before the 2 years were up (Sept 2024), with a confirmation email that the account was settled in full. Since then, they have been contacting me offering different products, but the calls begin with, "we are going to upgrade your decoder", my immediate response would be, "no you are not", I don't want it, I have since cancelled my Multichoice subscription. At the end of Jan 2025 the debited my bank account with an amount which I immediately had reversed. I have been trying to contact them to find out what this is for, they do not answer their telephones, and on email I get sent from one department to another and no-one is able or willing to assist me. I need to get them to cancel what ever debit order (which I never agreed to, since I have not done business with them) they have on their side.