ABSA wants me to pay R7,500.00 because I ran away because of monthly unauthorised (R99) debit orders

From 2017, every year my Absa Account i being debited 1 or 2 unauthorised debit orders of different amounts. I used to go to the bank every month to reverse these debit orders and every time I ask Consultant why this is happening I was told a new fix is coming where all debit orders will be authorised, till today unauthorised debit orders are still going on my account. So in November 2017, I left Absa and found myself a new bank that will not inconvenience me. In July 2018, ABSA started calling me and telling me I am owing them R7500 of banking fees. I have always been asking ABSA how did that happen, can I get a breakdown of amount making up the R7500. The call centre consultant will always refer me to the branch for further explanation as he's only calling to get the money and have no access to more information. I went to the branch in August and the consultant printed me the bank statement full of unauthorised debit orders and tell me that is how the R7500 came about, which up until today does not make any sense to me. I asked for further explanation and she said there is no further explanation what is on the bank statement is what I must pay.

Up until today, ABSA has not explained to me how am I owing them so much money for bank fees but because they are too powerful and arrogant they have decided to hand me over to a debt collector.