You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Gregory King.

ASSISTANT: How can I be a help for you Gregory?

USER: Unfortunately my travelling is postponed, so can you help me in changing my reservation?

ASSISTANT: Sure, it's my pleasure to help you. Sorry, there is no reservation found on your name.

USER: It's ok.

ASSISTANT: Thank you.Have a good day.

USER: Thank you.