You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Paul Smith. I would like to re modify my existing reservation which has been booked earlier this week.

ASSISTANT: Sure, I am here to help you. Give me a moment. I will check your previous reservation.

USER: Sure, please take your time.

ASSISTANT: Sorry Smith, there is no reservation is showing in our data base to change.

USER: It is ok. Thank you for the information.

ASSISTANT: Welcome. Thank you for choosing us.