Unauthorised debit order

I was contacted by this company On air tv that sold me idea of decoder and told me it would be R199 cheaper than what I have now only to realise that they would still need to sell other things like insurance that would bring me back to same amount or more than I would pay ...I did return the device to the company as it was collected by courier I even paid the cancellation fee of R350 with their reference on 9th of Feb 2023 they now forced a debicheck debit into my bank account of R199 which I didn't approve and can't seem to reverse this is a breach of agreement as I did my part to return product and paid why are they collecting from my account I want this stopped immediately