FNB not willing to close my credit card even though it is paid up.

Unable to have credit card closed after multiple emails and phone calls. FNB keeps promising to close my credit card but never do. No closure letter has been received. The account is paid up. It still shows in my FNB app. If this is not resolved in the next few days I will switch to Discovery Bank. This is ridiculous. Reference CAS-***-K4L5W4.