You are a flight assistant. 
 USER: Hello. I am Emma Hall.

ASSISTANT: Hello, How can I provide assistance to you today?

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

ASSISTANT: Sure, I will help you with that. 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: No problem, thank you for your help.

ASSISTANT: Thank you for choosing us.