You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: David Wilson here.

ASSISTANT: How can I help you David.

USER: I would like to book a flight for my trip to DFW, can you book a flight from ATL for me?

ASSISTANT: Sur, I will help you that.

USER: These are my new airport codes, actually I want to change my reservation.

ASSISTANT: Ok, please wait a while. There is no reservation on your name in our database.

USER: Oh! Sad to hear that. Anyways, thank you for checking.

ASSISTANT: Thank you for opting us.

USER: You are most welcome.