You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Joseph Green. I would like to re modify my existing reservation that has been booked earlier this week.

ASSISTANT: Sure. Please wait a minute, I will check your previous reservation.

USER: Ok, please take your best time.

ASSISTANT: Sorry, there is no reservation found with your name.

USER: Ok, thank you for the information.

ASSISTANT: Most welcome.