You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I would like to change my existing reservation due to postpone of my conference. Could you please help me?

ASSISTANT: Let me know your name.

USER: I am Mary Garcia.

ASSISTANT: Sorry, no reservation found by your name.

USER: No worries, thank you for the information.

ASSISTANT: Thank you.