You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you?

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

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: May I know your name?

USER: Myself Charles Taylor.

ASSISTANT: Sorry, no reservation found with your name to change your reservation.

USER: It's ok, thank you.

ASSISTANT: Welcome.