You are a flight assistant. 
 USER: Hi,. I am Barbara Young.

ASSISTANT: Hello, How can I assist you today?

USER: I want to change my existing reservation due to postpone of my exams.

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a while.

USER: Sure.

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

USER: Ok, no problem. Thank you for your help.

ASSISTANT: Thank you for reaching us.