You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, may I know your good name please?

USER: I am barbara Young.

ASSISTANT: Ok, how can I assist you?

USER: I want to change an existing reservation due to my  trip got postponed.

ASSISTANT: Please wait for a while.

USER: OK.

ASSISTANT: Thanks for your time. There is no reservation found with your name.

USER: Thank you for your response.

ASSISTANT: Thank you and have a good day.