Money deducted without any authorization or mandate

I am completely appalled that FNB can authorise attorneys to debit an amount of R6000 from my cheque account without authorization from me for my credit card which is in arrears and handed over to their "attorneys" the money that was deducted has caused considerable stress and anxiety as I was unable to provide basic needs for my family and extended family which I provide for. The Attorneys did not make any arrangement's or inform me of their planned deduction of my personal account which the bank allowed them to do. I have not authorized any deduction and neither do the attorneys have any mandate to deduct from my account. I will be escalating this to the payment association of south Africa as well as the credit and banking ombudsman as FNB has advised that they cannot reverse this money which was deducted. I am strongly considering leaving FNB as my money is no longer safe in my account if anyone can just demand or debit without consent or a mandate.