Korea to USA Free Trade Agreement?

Hello,

I shipped anime merchandise from Korea to myself in the USA so its usually just paper goods and small acrylic stands. Looking at the HTS it shows these items should actually be Duty Free from Korea due to the KORUSA Free Trade Agreement? Am I understanding something wrong like why am I still being charged for tariffs from FedEx? Country of manufacture/origin for these goods is South Korea so is this something I can dispute with FedEx?

And some more info, I called FedEx before the shipment even arrived to customs to try to explain how it should be KORUSA FTA but I just kept getting redirected to different departments. They even gave me a ticket number so I thought they took care of it. So I’m surprised a month later that I am getting this tariff bill from them.