The Seller should contact the shipping company immediately. He can go to the shipping company website to get the tracking information.
In cases in which the shipping company has lost the item, the Seller must offer a refund to the Buyer immediately and then file his loss claim with the shipper.
In cases in which the shipping company is claiming a delivery has been made, the Seller should ask for proof of delivery, which can be used to verify the correct address and name.
If the shipping company gives valid proof of delivery and the Seller has verified the name and address, then they has fulfilled their obligation. At this point, responsibility for resolution falls between the Buyer and the shipping company.
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