Worst worst worst customer service

Last week friday i deposited funds to nedbank for my loan,thats what i do every month. On sartuday they debited my accout,an amount of R5000 went off,my premium amount is R6000 which i paid already and not R11000 . I have been trying to call them since morning, eventually i went through and was sent from pillar to post,such ridiculous customer service. I need the extra amount refunded to me asap. This is ridiculous,how am i expected to survive the whole month if they deduct R11000