You are a flight assistant. 
 USER: Hello,. I am Benjamin Lopez.

ASSISTANT: Hi. How may I help you?

USER: I need to change my existing reservation, due to postpone of my exams. Can you please help me with that?

ASSISTANT: Sure, let me find your existing reservation.

USER: Sure.

ASSISTANT: Sorry Benjamin we didn't find any reservation on your name.

USER: Ok, no issue. Thank you.

ASSISTANT: Thank you.