Love **** them with kindness.
To the point, they cease to debate it after speaking in anger.

In other words, let not your mindest be controlled.

In church, where we find the best acting of pretense?
Put on a customer service performance that even God be impressed.

Think Jesus, think service.
Be so generous when the worst customer comes or approach you.

Show them, why you represent the company views?

Sure, sure for sure many customers you meet just not worth the effort of you being disgusted?

Remember, as an employee yours is based on performance.