How would you handle a customer who is unhappy about a bank policy?

"As a head teller for several years now, I'm accustomed to handling disgruntled customers. While the bank manager typically takes over if someone is extremely unhappy, I have learned how to deescalate situations on my own so I don't normally have to call over the bank manager. I am very careful about the tone of voice and body language I use. I also take particular care to use words that won't inflame the situation. I remain factual, professional, and respectful at all times. I am confident that I will be able to handle any and all unhappy customers as bank manager. While I'll stand firm on the bank's policies, I will explain them in a friendly, patient, and helpful manner."