You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Virginia Roberts.

ASSISTANT: Good afternoon, How can I help you?

USER: Actually, I planned to visit Washington DC for a music concert, but due to bad weather, the concert is postponed.

ASSISTANT: Would you like me to modify your existing reservation?

USER: Yes, please help me out.

ASSISTANT: I am sorry no reservation found on your name.

USER: That's ok.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your time.