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

ASSISTANT: Hello, how may I oblige you today?

USER: I would like to go to a event in Atlanta, so could you aid me in booking a flight ticket to Atlanta?

ASSISTANT: When are you planning to make your journey?

USER: Sure, I would like to go on Dec 18th and return back on Dec 20th.

ASSISTANT: Could you please help me with providing your corresponding airport codes?

USER: Sure, my source and destination airport codes are PHX and ATL respectively.

ASSISTANT: Sure, is there any another specifications on your trip, so that I can book a ticket as per your wish?

USER: Ensure it is a direct flight.

ASSISTANT: There is a direct flight found in Delta airlines with the fare 200.

USER: Ok, please proceed for further.

ASSISTANT: Your booking is done.

USER: Thank you for booking.

ASSISTANT: Thank you for reaching us.

USER: Welcome.