Unauthorized debit orders for On Air for Insurance

Dstv provide customer information to On Air who use our info to debit insurance policies on a a decoder. As if they do not make enough money, they still take money unauthorized from my bank account. I requested them several times to stop the debit order and to pay me back my money with interest, they confirmed cancellation, but just keep on debiting the money. And still do not pay me back. They just ignore my pleadings. What do they think???