You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you now?

USER: Unfortunately, I want to change my existing reservation can you please help me in this condition?

ASSISTANT: Sure, I will help you with that. Can I have the name on which you reserved earlier?

USER: Sure, my name is Nicholas Young here.

ASSISTANT: Ok, please wait a moment.

USER: Sure, I will wait.

ASSISTANT: Thank you for waiting.

USER: My pleasure.

ASSISTANT: Sorry Young, no reservation found under your name.

USER: Ok, no problem.

ASSISTANT: Thank you for choosing us, have a great day.

USER: Thank you for your information.

ASSISTANT: Most welcome.