You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Jessica Green. I want to change my existing reservation due to sudden change in my trip dates. Can you please help me with this?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Sorry to say, there is no reservation on your name in our database.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for opting us.