Unauthorized amount deducted from my account

I have a payment arrangement with FNB loans Consumer legal that on the 25th of each month they deduct R1747.03. I regularly pay every month, but this month they deducted twice without any consent or arrangement. I then went and reversed the one they double debited as I can't afford both to go off this month. They now have gone and deducted an amount of R575. When I called the call center to assist me the lady was not very helpful or friendly at all she would not reverse the amount or even be willing to assist me. I have had this issue before wih FNB and they wont reverse the money over the phone. You just get pushed from one department to another saying they not allowed to reverse the money, then holding on the line at least 30 minutes per department. Please can a Manager phone me urgently regarding this. I need that amount reversed ASAP.