You are a flight assistant. 
 USER: Hello. I am Alexander Davis.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, please wait for a moment. Sorry to say that, no reservation was found with your good name.

USER: Ok. No problem.

ASSISTANT: Thank you for reaching us.

USER: Thanks for the help.