You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you out?

USER: I am Robert Allen. I need to change my existing reservation, due to postpone of my live concert. Can you please help me?

ASSISTANT: Sure, I will help you  in changing the reservation. Sorry, there are no reservations found in our database.

USER: Ok, no issues.

ASSISTANT: Thank you for choosing us,.

USER: Thank you for your information.