You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Nancy Collins.

ASSISTANT: How can I help you at this moment.

USER: As my meeting got postponed, can you please help me in changing my existing reservation?

ASSISTANT: Sure Collins, I am here to help you to change your reservation.

USER: Thank you.

ASSISTANT: Can you give me a moment to check your previous reservation?

USER: Sure.

ASSISTANT: Sorry Collins, no reservation is found on your name to change your reservation.

USER: Ok, not an issue. May be something went wrong while booking the ticket previously. Anyways, thank you for providing information.

ASSISTANT: Welcome, thank you for choosing us.