You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: My name is Jack Jackson. I want to change my existing reservation due to postpone of my client meeting.

ASSISTANT: Sure, please be on hold.

USER: Ok.

ASSISTANT: Thanks for being on hold, no reservation was found based on your name in our database.

USER: No problem, thank you for your service.

ASSISTANT: Thank you for visiting us.