You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: My name is Katherine Hall. 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 wait for a minute, let me check the reservation details.

USER: Sure, take your finest time.

ASSISTANT: Thanks for your waiting, based on your request I could not find any reservation with your name in our database.

USER: Could you please check properly as I remember booking the reservation.

ASSISTANT: Yes, I check with your name clearly but I could not find any reservation with your name.

USER: Are you sure?

ASSISTANT: Yes Hall.

USER: It's fine, thank you for your time.

ASSISTANT: Thanks for choosing us.