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Using a card that is not your own amounts to illigality, so i think that if someone is trying to sell a card that has been issued to him back, to others the best thing to do is to shut it down. Because because it not morally.
So your say it is illegal to use cash as it does not belong to you.
Quadzillion company cards in use and how many wifes have used the husbands card?
I think what he was referring to was purchasing a card that was issued in someone else's name, like what is done on darknet markets, once they hack the victims' computers and steal their data.
Obviously, you can use the card of someone else if you have their consent.