You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you?

USER: I want to change my existing reservation, due to some health issues I have to change my reservation. Can you please help me in this condition?

ASSISTANT: Sad to hear, may I know your name please?

USER: Sure, my name is Sandra Green here.

ASSISTANT: Sorry Green, no reservation has been found on your name.

USER: Ok, that's fine.

ASSISTANT: Thank you for approaching us.

USER: Thank you for choosing us. Welcome.