You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Linda Lewis.

ASSISTANT: How can I aid you?

USER: Owing an emergency, I want do some changes in my existing reservation.

ASSISTANT: Sure, I will help you.

USER: Thank you.

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

USER: That's ok, thank you for checking.

ASSISTANT: Welcome.