You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Donald Anderson want  to book a ticket with price under 500, can you help me in booking flight ticket from Washington to San Francisco?

ASSISTANT: Sure, may I know your planned travel dates?

USER: Yes, I have planned to travel on 05/23 and return on 05/25.

ASSISTANT: Please share me your source and destination codes.

USER: Sure, my airport codes are DC-DCA and CA-SFO.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, we found an airline: Delta, flight number: 1018 with a single connection and price is 100.

USER: Ok, please proceed with booking.

ASSISTANT: Your flight ticket has been reserved.

USER: Thank you.

ASSISTANT: Thank you for choosing us.