buyer saying package not received, had tracking and signature with UPS

Canadian seller/buyer. Customer purchased product last week, was delivered to address on file and signed by different name via UPS. Amazon contacts me to provide customer with refund as they claim package was not received. Item is over $1000. Customer claims they contacted UPS and UPS says they delivered it to the wrong address, which is different than from what UPS told me. Likely assume this is buyer fraud as buyer is now saying it was a gift and needed it this weekend. No longer wants it and wants a refund.

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Buyer has not filed an A to Z claim and Amazon is pushing me to refund the buyer and take this up with UPS. I am a fairly new seller so need some help here please.