You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello,.

USER: I am Sandra Harris.

ASSISTANT: How may I be of your assistance?

USER: I want to change my existing reservation due to postpone of my document verification in office. Can you aid me in changing my reservation?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please be on hold for a while I will check the reservation list and get back to you with the status.

USER: Sure, I will wait.

ASSISTANT: Thank you for your time, I have checked in reservation list to change your details, but could not find any reservation with your name.

USER: Ok, not an issue. Thanks for your assistance.

ASSISTANT: Thanks for your approach. Hope to serve you again.