You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Andrew Lewis here.

ASSISTANT: How may I assist you?

USER: Due to sudden change in my planned dates, I would like to change my reservation. So can you please help me out to change my reservation?

ASSISTANT: Sure, please hold on a moment.

USER: Sure, take your time.

ASSISTANT: Sorry Lewis, no reservation has been found on your name in our database.

USER: Oh! Not an issue. Anyway, thank you for the information.

ASSISTANT: Thank you for using our service.

USER: Welcome.