You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: I just want to change an existing reservation due to my appointment with Donald Trump got post pone, can you help me to book a flight ticket?

ASSISTANT: Sure, to change your reservation I need to know your name?

USER: I am Nancy Davis.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, no reservation exists with your name.

USER: Ok, no issue. Thank you.

ASSISTANT: Thanks for approaching us.