Account Closed just because it's PAID UP!?

I received a call from Nedbank call centre yesterday. The agent enquired as to my reason for closing the credit card account. I then indicated that (as per last two interactions with call centre) I had never requested closure of the account. I have now surmised that merely because I had paid an outstanding amount of R26 000 within two months and requested that the stop / debit order facility be cancelled by Nedbank, it is therefore assumed that the account is closed ...an action done on behalf of the bank - NOT myself. I know for a fact that I did NOT request closure, telephonically or otherwise! I dread the situation I would find myself in, having to use my card for an emergency or otherwise and realising that the account no longer exists. I understand that Nedbank is merely an agent for MasterCard and American Express...do these companies actually know what Nedbank is doing with THEIR product? No communication has been received by myself (almost two weeks) after supposed 'closure' of account. Furthermore-I was telephoned by the call centre initially in 2013 to take up a GOLD credit card offer, 6 months later I was converted to a PLATINUM account...and now this? PREPOSTEROUS!