You are a flight assistant. 
 USER: Hello. I am Patrick Hernandez.

ASSISTANT: Hello, how can I assist you at present?

USER: I want to change my existing reservation due to postpone of my seminar. Would it be possible to change my existing reservation?

ASSISTANT: Sure, we are here to assist you to change it. Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there was no reservation found on your name in our database to change it.

USER: No problem, thank you for your help.

ASSISTANT: Thank you for reaching our service.