You are a flight assistant. 
 USER: Hello, I am Mark Lewis.

ASSISTANT: Hello, how may I help you?

USER: I would like to attend a friend's birthday bash in Washington, so could you please book a ticket?

ASSISTANT: Can I have your airport codes?

USER: My source and destination airport codes are PHL and IAD.

ASSISTANT: Please provide your desirous travel dates.

USER: I would like to go on 10/13 and return back on 10/15.

ASSISTANT: Please give me a moment.

USER: Ok, take your time.

ASSISTANT: There is a direct flight available with Southwest airlines, shall I book it?

USER: Ok, please proceed if it costs below 500.

ASSISTANT: Your ticket is booked, flight number is 1023.

USER: Thank you.

ASSISTANT: Thank you for reaching us, have a nice day.

USER: Welcome.