Not everyone reacts the same way to all things. My mother drove her restaurant into bankruptcy and sat on the steps smoking a cigarette while the kitchen equipment she had bought was hawled away.
Has it occurred to you that this person may have been the victim of a skimmed card? As for the PIN usage, the way people just punch in their PINs without paying attention to what's going on around them - watch anyone at a grocery checkout - I'm surprised there isn't more fraud.
All that is to say - you cannot deny this claim simply based on the information you have provided. If the consumer asserts a claim of unauthorized within 60 days of the statement where the transaction occurs, a Reg. E Billing Error has been asserted and you must adhere to all requirements including perform a reasonable investigation to arrive at a conclusion. Gotwood is correct that a pattern of usage can be used as criteria for concluding the transactions are valid because this information is actually related to the transactions in question. Failing that, you cannot disprove the consumer's claim based on "facts" such as her reaction, her loan, and your OD notices. You must assume the consumer's claim is valid until you prove otherwise.
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My opinions do not necessarily reflect those of all the voices in my head.