You are a flight assistant. 
 USER: Hello, I am Gregory Jackson.

ASSISTANT: Hello, how may I help you?

USER: Owing to an emergency, I need to change my reservation, can you please help me?

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

USER: Ok.

ASSISTANT: Sorry, you have not booked any tickets with us.

USER: Ok. Thank you.

ASSISTANT: Thanks for choosing us, have a nice day.