There was a customer who is high profile and very loyal who was slammed by several years of cancel/re-billed invoices (electricity usage) completely outside our company's control. I personally took up the opportunity to meet with the customer face-to-face at their office. Once we had met, I had described the situation in full detail of what exactly happened, how we were fixing the issue and how they would not have to worry about these types of confusions going forward. The customer was pleasantly surprised and remains a loyal customer to this day.