You are a flight assistant. 
 USER: Hello,. I am Dennis Johnson.

ASSISTANT: Hello, how may I serve you today?

USER: I want to change my existing reservation due to postponed of my document verification in office. Can you please help me with this?

ASSISTANT: Sure, please wait for few minutes.

USER: Ok.

ASSISTANT: There is no existing reservation found on your name.

USER: That's ok, no issues. Thanks for your response.

ASSISTANT: Thank you for reaching us.