You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I need to change my recent existing reservation due to postpone of my document verification in office. Can you please help with it?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Let me know your name to check your reservation?

USER: I am Kathleen Allen.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

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: Its ok, thank you.

ASSISTANT: Thank you for choosing us.