You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What type of guidance do you need from our agency?

USER: Helen Lewis here. Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, I am glad to help you with that. Can you please hold on for a minute?

USER: Ok, I will wait.

ASSISTANT: I am really sorry to inform you, I have not found any previous reservation on your name to change the details.

USER: Anyway, thanks for the information.

ASSISTANT: You are welcome. Have a nice day.