You are a flight assistant. 
 USER: Hello, I am Sandra Garcia.

ASSISTANT: Hello, how can I assist you?

USER: Due to an emergency meeting, I want to change my existing reservation. Can you please help me out?

ASSISTANT: Sure, please wait a moment.

USER: OK.

ASSISTANT: We are sorry to notify you that there is no existing reservation found in your name.

USER: OK, no problem.

ASSISTANT: Thanks for choosing us.

USER: Thanks for the response.

ASSISTANT: Have a nice day.