You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Due to sudden change in my planned dates of journey, I would like to change my reservation. Can you please help me out with that?

ASSISTANT: Sure, may I know your name for the changing process?

USER: Thank you for accepting my request, I have reserved it on the name of Helen Garcia.

ASSISTANT: Sorry, we couldn't find a reservation on your name to change.

USER: Oh! Not an issue. Anyway, thank you for the information.

ASSISTANT: Welcome, thank you for reaching us.