Once a PIN is entered, the transaction is completed and additional merchandise cannot be added after the fact without rerunning the card and reentering the PIN.
Prior to the cardholder entering her PIN at Wal-Mart, the pin pad displays the amount she is authorizing and she would have been given a the same receipt you obtained from Wal-Mart after completing the purchase.
The time for the customer to protest this amount was at the checkout counter. The customer authorized the $150 by entering he PIN at the time of purchase whether she realized it or not. Consequently, this situation does not meet the definition of an EFT error and you are free to deny the claim.
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