You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I am Dennis Lee. Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I am here to help you out. Please allow me a moment.

USER: Sure.

ASSISTANT: Sorry Lee, there is no active reservation on your name in our data base.

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

ASSISTANT: Thank you for reaching us.