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

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

USER: I want to postpone my trip due to an emergency. Can you help me to do some modifications in my existing reservation?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for a moment.

USER: Take your time.

ASSISTANT: Sorry, we found no reservation on your given name.

USER: No issues. Thank you for checking.

ASSISTANT: Thank you for reaching us.

USER: You are welcome.