Logged a request to close my Credit card 1 week ago, no actions has been takes

On The 22 January I called FNB premium banking requesting my settlement amount to close my credit card. Premium banking gave me my settlement value which I paid on the same day and call in again the same day to ask them to send a notice to the relevant credit card people to close my credit card. The Consultant I was speaking to told me that within 72 hours I would receive a call from them with regards to the closure. I didn't get any feedback or a call from no one I till I made follow ups on Thursday and another follow on Friday , this morning (29 January 2018) I get a statement that says I have R500 and something interest to be paid I called in and ask when was the interest generated they told me it was generated on Friday the 26th Jan2018. How is this possible ?I requested the account to be closed 4 days before you generated the interest and FNB didn't do its job so why should I now pay the interest? And I need to know what happened to the good, and speedy response service you promise your customers when you want them to take up a product with you. And what is more frustrating is that you don't call back to let me know on the status/ progress with regards to my request, all the time I have to make follow ups. I am very disappointed in you! Why does it seem like when you are about to loose a client you drag a process to close the account? If you want to retain me as a client give me a call make me a nice offer then I can decide whether I want to keep the account or what. I fee very disappointed by you!

my case number :cas- ********** -69X2k1