Nedbank Unauthorized double deduction

Unauthorized double deduction with no mandate, Called call center with no help ,I never consented to double deduction in the month of May, I have been in communication with them and have a payment plan. I need assistance to escalate this matter further it puts great strain on me financially and mentally. I need assistance please on how to sort this matter out asap .Currently left with zero balance on my account and have not bought any grocery for my kids,please help.