Disputed Cell C ********** Debit Order

Cell C **********ly deducted an amount of R265,04 on the 31st of August. I disputed and essentially blocked it. To my surprise, the same Cell C tried to deduct an amount of R980,46 yesterday. How did that happen after disputing and stopping that transaction in August? Now I had to pay a hefty FNB charges of R115 for having insufficient funds for something I knew that I disputed a month ago? This is so shocking. Time I move to different bank because clearly FNB don't take their clients seriously.