You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today from my end?

USER: I want to change my existing reservation, due to some health issue.  Can you help me?

ASSISTANT: Sure, I am here to help you out. Please provide me your name.

USER: Ok, my name is Sandra Nelson.

ASSISTANT: Sorry Sandra Nelson, there is no active reservation on your name in our database.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for reaching us.