You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I hand help to you?

USER: I am Rachel Wilson. I am planning to book a change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure, I can help you, please give me a moment.

USER: Sure, I will wait.

ASSISTANT: I am sorry to say that there is no reservation found for the user name to modify it. Have a nice day and thank you for reaching us.

USER: That's fine.

ASSISTANT: Most welcome.

USER: Thank you for your service.