You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: I want to change my reservation as my plan to visit Denver is postponed. Can you help me with that?

ASSISTANT: I will help you with that. May I know your name?

USER: My name is David Clark.

ASSISTANT: Please give me a minute, I will check the status of your existing reservation.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found under your name in our database.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for contacting us, have a nice day.