Hi.
user
Hello. How may I help you out?
assistant
I am Robert Allen. I need to change my existing reservation, due to postpone of my live concert. Can you please help me?
user
Sure, I will help you  in changing the reservation. Sorry, there are no reservations found in our database.
assistant
Ok, no issues.
user
Thank you for choosing us,.
assistant
Thank you for your information.
user