You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you?

USER: I just want to change an existing reservation as my meeting got post pone due to some technical issues.

ASSISTANT: Sure, We are here to help you.

USER: Can you please help me with this? Thank you.

ASSISTANT: May I know your name?

USER: I am Stephen Lee.

ASSISTANT: Give me a minute.

USER: Sure.

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: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.