If it's already showing on your credit report as a charge-off it's too late to pay it in order to get it reversed. Once you pay it, it will still remain on your credit report for 7 years before it drops off. I would suggest legal representation and investigation into a class action suit with other's that may be in a similar boat.
I'm suprised as a platinum card member that Amex would think you don't have the resources to prosecute this case.