You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I am Rachel Brown. 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 Rachel, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say that, there is no reservation found on your name.

USER: No issues, thank you for your time.

ASSISTANT: Thank you for approaching us.