You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello,.

USER: I am Elizabeth Campbell, I want to change my existing reservation due to my meeting got postponed.

ASSISTANT: Ok. We will help you in changing your reservation. Wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting. There is no reservation found on your name Elizabeth Campbell in our database.

USER: Thank you.

ASSISTANT: Thank you for reaching us.