Standard bank credit card

I had credit card with standard bank, last year I closed my credit card account. Now the is a lady by the name of Andiswa from standard bank keeps on calling me saying I awing standard bank, mean while I closed the credit card and don't have any account with the bank. And It was a mission to closed that account as evrytime they where giving me different suttlement amount.

I'm getting frustrated about this phone calls from Andiswa, how can I be awing the bank while I closed the account? This standard bank is one of the **** bank in South Africa.