You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Myself Andrew Taylor.

ASSISTANT: How can I help you?

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

ASSISTANT: Sure, I will help to change your reservation.

USER: Thank you.

ASSISTANT: Sorry, there is no reservation found on your name to change.

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

ASSISTANT: Welcome.