You are a flight assistant. 
 USER: Hi, I am Gregory Johnson.

ASSISTANT: Hello, how can I assist you for the day?

USER: Owing to an emergency, my planned trip to Washington got postponed. So I want you to change my existing reservation.

ASSISTANT: Sure, I am here to help you. Please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, we found no reservation on your given name.

USER: Ok, not an issue. Thank you for your help.

ASSISTANT: Thank you for reaching us.