You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Timothy Lee. I am planning to book a ticket from CLT to SFO. Can you please help me out?

ASSISTANT: Sure, I will help you with that. Please provide me your trip dates.

USER: I would like to travel on 05/12 and return back on 05/14.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry Lee, there is no flight available on your preferred dates.

USER: That's fine. Thank you for your service.

ASSISTANT: You are most welcome.