You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: I would like to change my existing flight reservation that has been booked earlier this week.Could you please help me in re-modifying my dates in the reservation?

ASSISTANT: Sure, please help me by giving your name so that I can you easily by checking your reservation.

USER: Thank you for considering my request. I have done my reservation under my name Emma Martinez.

ASSISTANT: Wait a moment, let me check.

USER: Sure.

ASSISTANT: Sorry to inform you, there is no previous reservation found under your name to change it.

USER: It's ok, anyway thank you for the help.

ASSISTANT: My pleasure, have a good day.