Credit limit decrease and Nedbank took all my extra cash!

I app**** for a credit limit increase on my credit card after receiving a message to say that I qualify for a limit increase. I then contacted Nedbank and now all of a sudden my limit was decreased. I have always paid my credit card. I transferred all my extra cash to my credit card and now there is nothing left! I am furious! Why would they just decrease my limit if I always honor paying my account!