Unauthorised Debit Order

Discovery Card debited my account with R11 700 without my concern and when I ask for the debit order to be reversed they said they cant. I know my account has been in arrears but I was retrenched and unemployed. This is not the only debt that Im paying and how can you take R11 700. This leaves me in insufficient funds to pay for my Bond, vehicle finance and other commitment. I phone their Call Centre at 08h40 on the 21/12/2018 and a lady by the name of Tebogo was so arrogant and told me that I need to pay and they wont do any reversal. Please help