Requested double payment after loosing parcel and then returned package to sender

After having paid import duty and taxes on my parcel FedEx then claims that it never entered the country, my import duties and taxes were not refunded. My supplier had to ship another package at their own expense and FedEx again requested I pay import duties and taxes for a second time. When trying to contest this second duties and taxes payment they handed me off from one department to another until a point where they returned my package to the supplier. Hence I have paid premium delivery fees for an international priority shipment, import duties and taxes on a shipment that never arrived and now FedEx have returned the shipment to sender. Will never use this service again.