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by greenyoda
3387 days ago
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If you have the last 4 digits of someone's credit card number, you could ask them to perform a transaction with that credit card, which would require them to know the complete credit card number, not just the last 4 digits. (Once you've confirmed that they are the credit card holder, you can let them cancel the transaction.) Also, if they've made credit card transactions on your site in the past, you would know their billing address. You could send a letter to that address with an authentication code that they can read back to you to confirm that they've received it. |
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