You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you out?

USER: I have booked a ticket on my name  Nicholas Smith, so please help me in ticket booking changing?

ASSISTANT: Sure, I will help you in changing the reservation.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there are no reservations found.

USER: Ok, that's fine, thank you for your information.

ASSISTANT: Thank you for choosing us.

USER: Welcome.