You shouldn't take someone's credit card.
Will is at the store, but isn't sure he has enough money for the things he wants to buy, when he spots a lost credit card on the floor.
Will wants to buy what he can from the store.
Will turns the credit card into the lost and found and buys what he can with the money he has.
Will uses the credit card to buy the things he wants.
Will gets what he can from the store, and the credit card owner gets their card back.
The credit card is reported stolen, and it is traced back to Will, who is arrested.