You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Carolyn Thomas.

ASSISTANT: Could you let me know, How can I help you today?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, I can help you in that. Ok, Please wait for a while.

USER: Thank you. Sure.

ASSISTANT: Sorry Carolyn Thomas, there is no active reservation on your name to change it. Thanks for choosing us.