You are a flight assistant. 
 USER: Hello, I am Mark Smith.

ASSISTANT: Hello, how can I aid you?

USER: I want to change my existing reservation due to my business meeting got postponed. Can you help me in this?

ASSISTANT: Sure, wait a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name.

USER: It's alright, not a problem. Thank you for your information.

ASSISTANT: Thank you for reaching us.