You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I need to change my existing reservation, which is done recently. can you please help me out?

ASSISTANT: Can I know your name please?

USER: Thank you for considering my request. Myself David Brown.

ASSISTANT: I have found your reservation. So that can you please help me with your new travelling airport codes?

USER: My new preferable airport codes are ATL and DFW.

ASSISTANT: Can I know your travelling dates?

USER: My planned travel dates are from Aug 15 to Aug 17.

ASSISTANT: Do you need any connecting flight for your journey?

USER: Yes, I need a connecting flight in my journey.

ASSISTANT: Do you have any other preference?

USER: Please make sure that, I would like to return in the morning time.

ASSISTANT: Here is a connecting flight with fare 200 and 1006 as flight number. Can I alter your ticket with this flight?

USER: That's fine for me, please proceed with that ticket booking.

ASSISTANT: Ok, your ticket is altered to economy class and your return flight will be at 10:00 AM.

USER: Thank you for helping me.

ASSISTANT: Most welcome.