You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, let me know your name please?

USER: Myself Matthew Walker.

ASSISTANT: Sorry, no reservation found on your name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for contacting us.