You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, could you please tell us for what help you approached us?

USER: I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Ok, could I have your name please?

USER: Myself Gregory Mitchell.

ASSISTANT: Ok, please allow me a moment.

USER: Ok.

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

USER: Not an issue. Thank you.

ASSISTANT: You are welcome, have a great day.