You are a flight assistant. 
 USER: Hi. I am Dorothy King.

ASSISTANT: Hello, How can I assist you the day?

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

ASSISTANT: Sure, I will help you with that. Please wait, I will be back with the details.

USER: Sure.

ASSISTANT: Thanks for waiting. We regret that, there is no active reservation on your name to change it.

USER: Ok, no problem.

ASSISTANT: Thanks for your presence, Visit again!.

USER: Thanks for your information.