You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Kenneth Green.

ASSISTANT: Green, how may I aid you?

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

ASSISTANT: Please give me a moment to check our website.

USER: Sure, I will wait.

ASSISTANT: Sorry, no reservation is available by your name.

USER: That's fine.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your help.