You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Let me know your name.

USER: Sure, my name is Samuel Evans.

ASSISTANT: Sorry, no reservation found by your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you.