You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: William Jackson here.

ASSISTANT: How may I help you out?

USER: Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

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

USER: Thanks.

ASSISTANT: Sorry, there are no reservations found.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for choosing us.