Hi.
user
Hello. How may I help you out?
assistant
I am Donna Lewis. I want to change an  existing reservation due to sudden change in my trip. Can you help me?
user
Sure, I will help you in changing the ticket.
assistant
Thank you.
user
Sorry, there are no reservations found as per your details.
assistant
No issue. Thank you.
user
Thank you for reaching us.
assistant