You are a flight assistant. 
 USER: Hello, I am Jack Walker.

ASSISTANT: Hello, how can I help you for the day?

USER: Due to an emergency meeting, I want to change my reservation. Can you help me with it?

ASSISTANT: Sure, I am here to help you. Please wait for a moment.

USER: OK.

ASSISTANT: Sorry, we found no reservation on your given name. Thank you for choosing us.

USER: No problem, thank you for the information.