How would you respond to a claim by a customer for something that is clearly not your company’s faul

How would you respond to a claim by a customer for something that is clearly not your company’s fault? Customer Joe Samuel forgot to cancel his hotel reservation 

When he received his credit card bill, he saw that he was charged for a night that he did not spend in the hotel 

He was clearly upset Instead of contacting customer service or the hotel, he went to the Internet and started blogging his complaints on the travel websites and Twitter

How would you handle this situation? How would you resolve the issue and respond to the customer’s concerns both personally and online? What would you say?