You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: Please help me to change an existing reservation as my trip got post pone.

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Could you please forward your name for checking purpose?

USER: I made a reservation by this name Charles Collins.

ASSISTANT: Sorry, no reservation found on your name in our records.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for choosing us, have a great day.