Debiting money and signing me up with a car insurance without my consent.

Absa car finance is debiting money from my account without my permission. They financing my car and my monthly premium is R3100 however i asked them to debit me R4100 monthly so that I can finish paying them earlier. So this is what happened, end of August they debited R5200 and I went to the bank to reverse the money and i blocked them fron debiting from my account. I saw it best to pay them myself every month unlike them taking money from my account without my knowledge. Now i paid the R4100 and later on they sent a message saying that my loan is in errors of R900, i called them to find out what are talking about. It came to my attention that they somehow signed me up with their car insurance without talking to me and getting my approval. Im so ****ed right now I'm even thinking of suing them cause what they did is not acceptable.