You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I am Brandon Martinez. Please change my existing reservation as my trip got postponed.

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please hold on.

USER: Sure.

ASSISTANT: Thanks for your precious time, there is no reservation found on your name to change.

USER: Ok, Not an issue. Thank you.

ASSISTANT: Thank you for choosing us.