You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I just want to change an existing reservation as my meeting got post pone due to some technical issues. Can you help me?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please let me know with your name.

USER: Cynthia Moore.

ASSISTANT: Please allow me a minute to check for your booking details.

USER: Ok.

ASSISTANT: Thank you. Cynthia Moore, I have found your flight booking details. Please help me with your depart and arrival airport codes.

USER: DCA and CLT are my airport codes.

ASSISTANT: Please let me know with your re-planned travelling dates.

USER: 11/23 and 11/25 are my travelling dates.

ASSISTANT: Please help me with your preferred class to fly.

USER: There are no preference in class.

ASSISTANT: Do you prefer to have a break in your journey?

USER: No.

ASSISTANT: To help you better, please let me know if you have any other preferences in your journey.

USER: I don't have any other comforts.

ASSISTANT: Thank you for letting me know.

USER: Ok.

ASSISTANT: Please allow me a minute.

USER: Sure.

ASSISTANT: Cynthia Moore, I am really sorry to inform you that there are no flights available for your journey.

USER: No issue. Thank you.