You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, wait a minute.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found on your name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for choosing us.