You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you today?

USER: I am Donald Green. I want to change my existing reservation due to health issues, can you please help me in that?

ASSISTANT: Sure, I will help you with that. Please wait for a minute.

USER: Ok.

ASSISTANT: I am sorry to say that there is no reservation found under your name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for reaching us.