You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Justin King here.

ASSISTANT: How can I assist you?

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

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

USER: Thank you.

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

USER: It's ok, no problem.

ASSISTANT: Ok.

USER: Thank you for your information.

ASSISTANT: Welcome. Thank you for choosing us.