You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: My name is Barbara Harris.

ASSISTANT: Ok.

USER: I want to change my existing reservation, can you help me for that?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please wait a moment.

USER: Sure, take your time.

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

USER: Thank you.

ASSISTANT: Thank you for reaching us.

USER: Welcome.