You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Thomas Anderson.

ASSISTANT: How can I help you?

USER: I would like to change my existing reservation, due to some health issues. Can you please help me with this?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Please give me a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: Ok, not an issue. Thank you for the information.

ASSISTANT: Welcome. Have a nice day. Thank you for choosing us.