Nedbank refuses to assist us or to even provide us with credible reasoning on decline in credit limit increases

referenc: FI***. I have called in for a credit limit increase or to get an American Express card but I am constantly been declined based on affordability yet I have checked credit bureau and I dont have any affordability issues, I have recently paid my standard bank credit card off and if that is updated on the bureau then I have less than 20% debt. I am banking with Nedbank for many years yet they refuse to assist me but other banks are willing to provide these services to us, so I feel Its pointless banking with nedbank if they dont want to assist us with credit.