You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you today?

USER: This is Helen Nelson.

ASSISTANT: Ok.

USER: I want to change an existing reservation due to some health issues. Can you please help me in that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name in our reservation database.

USER: Ok, no problem.

ASSISTANT: Thank you for choosing us, have a nice day.

USER: Thank you for your service.