Disgusted with Nedbank!!

I charged R4000 deposit to my credit card for STA travel, I lodged a charge back request, sent all the supporting docs as well, only to be told they cannot do a charge back. I have been reading posts on Social media and don't understand why some people have received chargebacks, yet mine has been declined!!!!! Its the same bank, so why approve some and not others!!!!!! I have been a loyal Customer to Nedbank for many years, even my home loan is with Nedbank, I am disappointed with the outcome of my request and disappointed that I was basically told that I don't have leg to stand on as I need to take this up with the merchant that is LIQUIDATED!!!!!!! Disgusted. Why treat clients differently!!!!