You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you out?

USER: I am Donna Lewis. I want to change an  existing reservation due to sudden change in my trip. Can you help me?

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

USER: Thank you.

ASSISTANT: Sorry, there are no reservations found as per your details.

USER: No issue. Thank you.

ASSISTANT: Thank you for reaching us.