You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I guide you?

USER: I am Dorothy Baker. I would like to change my existing reservation. Could you please help?

ASSISTANT: Sure, can I know your preferable dates?

USER: I would like to travel on 03/23 and return back on 03/25.

ASSISTANT: Please hold on for a moment, let me check.

USER: Ok, please take your time.

ASSISTANT: I am sorry, there are no reservation with your name.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you for your time.