Credit card declined for no valid reason

I have done a credit card application and was told that its declined as there was an existing credit card account on the system which was eventually closed, got assisted By Dudu at the Cresta branch with resubmitting the application via client switching department, I got feedback from Dudu that the application was declined, she then enquired on the reason and was told its because of affordability. Id like to find out how am I not approved when my income is paid into FNB and they can clearly see the and are offering me an upgrade to Private client but fail to offer me a credit limit even if theres a minimum amount. I do not understand what criteria is required to get approved as I know I have a good credit score and disposable income to be able to AFFORD for the repayments. Can someone reassess my profile and give me feedback and clarity as it really doesnt make any sense. Also want to note that Dudu has been helpful during this process and has tried all she could to assist but I believe someone higher must intervene. I get approved for everything except a credit card *WHY*??