Remember, the 'customer' is always right. [=never argue with a customer]
He is one tough/tricky 'customer'. [=he is a tough/tricky person]
The company has good/poor 'customer' service.
(..) - Vultures everywhere. Thanks. - Goodbye. It has been a pleasure to meet you. I'm sorry. You are getting to be your best customer. Well, drinking! I'm very pleased with you. You're beginning to live like a Frenchman. That's some going-over (..)1942 Casablanca