Penalty Charge which wasn’t my fault

I bought a radio for my car on Aliexpress on 1 April 2023. The radio was sent via FedEx from China for me to receive on the 14 April 2023 as per the estimated date. Customs received the radio on the their side there were issues. I was asked for proof of payment aswell the literature of which I submitted. Now I am being told that the seller has made errors on the package and I am being charged a penalty of R1500. I don’t understand why should be charged such amounts i only bought and not responsible on the mistakes the seller makes with FedEx and why it not charged from the seller. How should I know as a buyer that the seller has made some mistakes? Secondly I am being charged TAX twice at first before the package arrived to SA i was charged R663.03 and now I am charged again an additional R709.80. How does this work? Can I be assisted because I have been sending emails for the past 14 days and making calls to FEDEX but I am not happy with the response and treatment.