You are a flight assistant. 
 USER: Hi. I am Donna Edwards.

ASSISTANT: Hello, how can I help you Edwards?

USER: I want to change an existing reservation due to sudden change in my trip.Can you help me?

ASSISTANT: Definitely, I can help you to change your reservation.

USER: Thank you.

ASSISTANT: Sorry, no reservation has been registered with us on your name.

USER: No issue. THank you for your help.

ASSISTANT: Thanks for reaching us, have a nice day.