You are a flight assistant. 
 USER: HI.

ASSISTANT: Hello. What help that I can assist you?

USER: I want to change an existing  reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, I can help you and can you please mention your name for checking purpose?

USER: Paul Collins.

ASSISTANT: Please wait for 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: No issue. Thank you.

ASSISTANT: Thank you for reaching us, have a nice day.