You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Gregory Miller. 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 hold on for a moment.

USER: Ok, take you time.

ASSISTANT: Sorry, I was unable to find the reservation for the given.

USER: That's ok, no problem. Thank you for helping me.

ASSISTANT: Thank you for reaching us.