You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

USER: I would like to change my previous travel dates, which is done recently. Can you please help me out?

ASSISTANT: Sure, could I have your name please?

USER: Thank you for considering my request.

ASSISTANT: Ok, please allow me a moment.

USER: Myself Christine Nelson.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes further.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: You are welcome, have a great day.