You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you at this moment?

USER: Can you please change my existing reservation?

ASSISTANT: Sure, I am happy to help you with that.

USER: Thank you.

ASSISTANT: Can I have your good name please to check your reservation status?

USER: I am Stephen Robinson here.

ASSISTANT: Ok, please wait a moment.

USER: Sure, I will wait.

ASSISTANT: Sorry Stephen Robinson, no reservation has found under your name to change.

USER: Ok, not an issue.

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

USER: Thank you for your help.

ASSISTANT: Most welcome.