Nedbank just cancelled credit card & demanding full payment

I have just received my statement, I have never been in the arrears and now they demanding the full amount owing on the credit card. I phoned the call centre to find out if there was a mistake only to be told that this has been handed over to legal and they cannot assist me. I could not believe this, its a disgrace. I get put through to legal and choose option 1 to leave a message as I have already been holding on for some time, the recorded voice says we unable to assist you please call back during office hours, it is 12:45 on 30th April. I am struggling to get answers, non of the customer consultants can assist