You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Jason Miller.

ASSISTANT: How can I help you?

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

ASSISTANT: Sure, I will help you.

USER: Ok.

ASSISTANT: Sorry to inform  that there is no reservation on your name.

USER: Ok, No issues. Thanks for sharing information.

ASSISTANT: Thank you for approaching us.