You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be there for you?

USER: I am Katherine Hill. I want to change my existing reservation due to health issues, can you help me in change reservation?

ASSISTANT: Sure, let me check the data base and revert you.

USER: Ok.

ASSISTANT: I have gone through the reservation list but could not find any reservation by your name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.