You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am David Thompson.

ASSISTANT: How can I assist you today?

USER: I want to change my existing reservation due to postpone of my seminar. Could you please help me?

ASSISTANT: Sure, please give me a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

USER: No worries, thank you for the information.

ASSISTANT: Welcome, have a great day.