You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Timothy Hill.

ASSISTANT: How can I assist you today?

USER: I want to cange my existing reservation due to my meeting got postponed. Can you help me to change reservation?

ASSISTANT: Sure. Please wait for a moment, I will check and get back to you.

USER: Sure.

ASSISTANT: Thanks for waiting. Sorry, no reservation found with your name.

USER: OK, No problem.

ASSISTANT: Thanks for choosing us.

USER: Thanks for the information.