You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Alexander Perez.

ASSISTANT: How may I assist you?

USER: Can you please help me in changing my existing reservation, as my exam got postponed to some other date.

ASSISTANT: Sure, I am here to help you with that.

USER: Thank you.

ASSISTANT: Wait a moment please. Alexander Perez, we regret to inform you that there is no reservation found on your name in our records.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for reaching us.