You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: May I know your name please?

USER: Sure, my name is Dorothy Jackson.

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

USER: Ok, no problem. Anyways, thank you for your service.

ASSISTANT: Thank you for opting us.