You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I support you?

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

ASSISTANT: Sure, I can help you. May I know your name to check in the reservation list?

USER: Myself Helen Roberts.

ASSISTANT: Please wait for a second.

USER: Ok.

ASSISTANT: Sorry, we couldn't find any reservation with your name. Thanks for approaching us.

USER: Thank you so much for your kind help.