You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I support you today?

USER: I am Donald Green. Owing to an emergency, I want to change an existing reservation. Could you help me in changing the reservation?

ASSISTANT: Sure, I am here to help you. Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found on your name to change.

USER: Not an issue. Thank you for your information.

ASSISTANT: Thank you for choosing us.