You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I be of your help?

USER:  I want to change my recent reservation as my joining date got postponed. Can you help me in changing?

ASSISTANT: Sure, I'll try to help you in changing an existing reservation.

USER: Thank you for accepting my request.

ASSISTANT: Please let me know your name to check the reservation list.

USER: My name is Rachel Smith.

ASSISTANT: Thank you for providing your name , please wait a moment.

USER: Sure.

ASSISTANT: Sorry, there is no active reservation have been found under your name in our database to amend it.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for approaching us.