Dstv taking money from bank account without permission

I did away with dstv months ago and I mo longer use the decoders etc and I was on month to month basis with dstv meaning I paid monthly eft payment and never gave them my banking details to debit my account then out of the blue they debit my account last month for 679rand and I havnt watched dstv for months..when I called the call centre they lady says she does not know why they did that and assured me that it won't happen again as I told her I did not give them permission to debit my account so who told them debit it.. she said the money will be returned and promised me that no other debits will go off as she sorted it out on the system..i reversed the payment on my banking app and that was that..then this month they debit again..so they are a bunch of ******..they taking money from my bank account with permission.