You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Mark Nelson. Owing to an emergency, I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Sure, please hold on a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on given name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for reaching us.