Unauthorised debit order.

I had a 2 year contract for a DSTV Explora decoder, which ended in Oct 2023. My final payment was in Nov 2023. In Dec 2023 I received an SMS notifying of a pending deduction. I phoned the number on the SMS to advise that my contract with them had ended and was assured there would be no further deductions. OnAir TV have just deducted R89.00 from my account again - without my authorisation. Looking at reviews, it seems that I'm not the only victim.