You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I assist you?

USER: I am Jacob Lee. Owing to an emergency, I want to change my existing reservation. So please help me in changing the existing reservation.

ASSISTANT: Sure, Please wait a second.

USER: Ok.

ASSISTANT: Sorry, No reservation found on your name.

USER: Not an issue.

ASSISTANT: Thank you for opting us.

USER: Thank you.