I've been a service crew for almost 2 years and facing a customer with different attitudes is really something.Some customers are polite and friendly, and there are some who are too proud.
They don't want to be corrected or even accepts suggestions.
And what happens is, this saying always implies:
"The customer is always right."

I don't really believe in that.
Even our managers don't. But for business' sake, they do follow.
I hate explaining, especially if we commits mistakes.
But what's more degrading is that, there are some people who are just maybe too proud that they think they can buy everything that they see and that money can gives them power to step on other people and you have nothing to do but to say "sorry".

Do you believe that the customers are always right?