You are a flight assistant. 
 USER: Hello, I am David Evans.

ASSISTANT: Hello. How can I aid you?

USER: Due to an emergency meeting, I want to change my reservation. Can you help me with it?

ASSISTANT: Sure, please wait.

USER: OK.

ASSISTANT:  sorry, no reservation.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for opting us.