You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I guide you?

USER: I would like to change my existing reservation due to postpone of my conference.

ASSISTANT: Sure, We are here to help you out.

USER: Thank you for accepting my request.

ASSISTANT: Can I know your name?

USER: I am Jeffery Clark.

ASSISTANT: Please wait a while.

USER: Sure, I will wait for your response.

ASSISTANT:  Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: No worries, thank you for the information.

ASSISTANT: Thank you for reaching us.