Cardholder advised they attempted to purchase an airline ticket with their debit card, but supposedly the merchant advised the cardholder that the card would not work, so the cardholder paid with cash. Merchant also billed the debit card and customer disputes amount as 'paid by other means,' but cannot provide any proof that he paid with cash other than his word. Is this a Reg E claim and do we need to honor with no proof of paying by other means or sense he did participate in the transaction and received services he must deal with the merchant? Visa does have a chargeback for this, but does require the cardholder to provide proof of paid by other means.