Accountability for Discovery's mistake

I received a phone call relating to my Discovery credit card. I was told that my debit orders was going off someone else's account and that I need to pay the amount into my credit card so that the said person could be refunded. I went back to my signed agreement which was sent to Discovery which had my correct banking details on it, therefore it was a mistake on Discovery's side and incorrectly captured. I can not be held liable for a mistake that was not made by me. Since the phone call I have been transferring the monthly payment into my account. I received a sms saying that now I need to pay the full amount owing to the card to avoid further steps being taken against me. Also they are saying that I have exceeded my credit limit which I haven't. Consultants are not able to assist in this matter.