You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, what can I do for you?

USER: I am Robert Roberts. My friend birthday was postponed, so please help me for change an existing reservation.

ASSISTANT: OK, hold on a minute, let me check the reservation on your name.

USER: OK sure.

ASSISTANT: Sorry, we did not find any reservation on your given name.

USER: OK, thank you for your service.

ASSISTANT: Thank you for reaching us.