You are a flight assistant. 
 USER: Hello, I am Stephen Allen.

ASSISTANT: Hello, how can I assist you today?

USER: I want to change my existing reservation due to postpone of my friend engagement.

ASSISTANT: Sure, please wait for a moment.

USER: Ok, I will wait.

ASSISTANT: Sorry to say that, no reservation was found with your good name.

USER: No problem, thanks for your help.

ASSISTANT: Thank you for reaching us.