You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Christine Williams.

ASSISTANT: Yes, Williams.

USER: I am planning to change an existing reservation, due to health problem. Can you please change my reservation?

ASSISTANT: Sure, I will help you out.

USER: Sure, take your own time.

ASSISTANT: Sorry Williams, no reservation found on your name.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for reaching us.