You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you for the day?

USER: Could you please change my existing  reservation due to postpone of my trip?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: May, I know your good name?

USER: My name is David Smith.

ASSISTANT: Sorry, we found no reservation on your good name?

USER: Not a problem, thank you for checking.

ASSISTANT: Thank you for reaching us.