When i was working on an E-commerce company, i once received a call from a customer that claim that his order hasn't been delivered even though the payment is already made.
To handle this, i first make sure that the order is correct by asking the distribution office.
As it turned out, the distribution office make a mistake in filling the purchase order, so i sincerely apologize to the customers and offer his money back.
The customer told me that it's okay and tell me that he's glad that i was being honest about the whole thing.