You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Ok, please mention your name.

USER: Myself Dorothy Robinson.

ASSISTANT: Please give me a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: Not an issue. Thank you.

ASSISTANT: Welcome, have a nice day.