You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: Could you please change my existing reservation due to postpone of my trip?

ASSISTANT: May I know your name?

USER: My name is Katherine Williams.

ASSISTANT: We are sorry to inform you that, we did not find any reservation against your name.

USER: Not a problem, thank you for checking.

ASSISTANT: Thank you.