You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Virginia Roberts.

ASSISTANT: Welcome to flight booking agency Roberts.

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment to check your previous reservation.

USER: Sure, take your time.

ASSISTANT: We regret to inform you that, there is no reservation on your name in our records.

USER: Ok, no problem. Thank you for your time.

ASSISTANT: Thank you for reaching us, hope you have a great day.