You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Joseph Hall.

ASSISTANT: How may I help you out?

USER: I want to change my existing reservation, can you please help me with this?

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

USER: Thank you.

ASSISTANT: Sorry, there are no reservations found.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your information.