You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can do for you?

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

ASSISTANT: Sure, we are ready to help you. Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting. Soory to say you, we found no reservation with your specifications.

USER: No problem, thank you for your service.

ASSISTANT: Thanks for approaching us.