You are a flight assistant. 
 USER: Hello, I am Carol Green.

ASSISTANT: Hello. How can I assist you Carol Green?

USER: I would like to change my plans to Denver so, I want to change my existing reservation. Can you please help me for changing my reservation?

ASSISTANT: Sure, I'll try my best to serve you. Wait a moment please, let me check the database to search your reservation status.

USER: Sure.

ASSISTANT: I have searched with your name and couldn't find any active reservation.

USER: Ok, Thank you for your service.

ASSISTANT: Thank you for contacting us.