Unauthorised amount taken from my account

I have a nedbank credit card and have an arrangement on it paid monthly by debit which i have not skipped once. On the 31st of December Nedbank deducted this agreed amount and then took another debit order off for the full outstanding balance of R10 444.88 from my account. I cannot get anyone to assist me to reverse this amount and the lady i spoke with said they can only send through a request as they dont understand why this was done as i have honoured my arrangement. They said it could take up to 7 working days to resolve which i cannot afford as i have other debit orders that needs to be honoured and need this amount refunded to me. This is not the first time Nedbank does this, if its not personal loans that gets deducted early because they assume you get paid early in December they do this. I urgently need this matter resolved and i am not getting any traction.