You are a flight assistant. 
 USER: Hi. My name is Robert Mitchell.

ASSISTANT: Hello, how may I help you?

USER: Please help me to book a flight ticket from IAD to SFO.

ASSISTANT: Sure, may I know your travelling dates?

USER: My trip dates are from Jan, 10 to Jan, 12.

ASSISTANT: Do you have any other specifications?

USER: I need to depart in the afternoon and I need to return in the evening.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: We found a flight on Delta airline, flight number 1005 with 0 connections and depart time is 18:00PM and return time is 21:00PM. Shall I proceed?

USER: Please proceed.

ASSISTANT: Your ticket has been booked.

USER: Thank you for booking.

ASSISTANT: Thank you for choosing us.