You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Alexander Smith. Can you please assist me in booking a flight ticket from IAD to OAK?

ASSISTANT: Sure, I will help you in booking the ticket.

USER: Thank you.

ASSISTANT: May I know your travelling dates please?

USER: My travelling dates are 10/25 and 10/27.

ASSISTANT: Please wait a moment.

USER: Ok, take your time.

ASSISTANT: Sorry, there are no flights found.

USER: It's ok, thank you for spending your time in checking the flight for me.

ASSISTANT: Thank you for choosing us.