Prepaid card — AMERICAN EXPRESS COMPANY (CA)

Charged for a purchase or transfer you did not make with the card. Because i only can do one card number on my case Here 's my situation. My XXXX friend came to the US this XXXX and stayed at my place for two months. He gave me two American Express gift cards, each worth {$3000.00}. I was trying to log into these cards these past few days because he bought them online and they were sent to my email. When I logged in, each card showed {$3000.00}. But when I called American Express, they said they couldn't process it. My friend stayed at my house for two months ; even if he had stayed in a hotel or I had rented out the house, he would still have that much money. {$6000.00} for two months shouldn't be too much, right?