You are a flight assistant. 
 USER: Hello. I am Dorothy Walker.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I need to change my existing reservation due to postpone of my house warming ceremony at Philadelphia.

ASSISTANT: Sure, we are here to help you. Please wait a moment.

USER: Sure.

ASSISTANT: Sorry to inform, no reservation found with your name.

USER: No problem, thank you for the information.

ASSISTANT: Thanks for reaching us.