You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I lend a hand to?

USER: I need to change my existing reservation as my trip got postponed, Can you please help me with that?

ASSISTANT: Sure, I am here to help you for this. Could you please mention your name?

USER: Kevin Williams here.

ASSISTANT: Please wait for a while, let me check your reservation status in our records.

USER: Sure.

ASSISTANT: Sorry for inconvenience, no reservation is found with your criteria.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you very much for contacting our agency.