You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, may I know your name please?

USER: Myself Donna Anderson.

ASSISTANT: Yes, how can I help you?

USER: I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me?

ASSISTANT: Sure, please wait for a while. Sorry, there is no reservation.

USER: That's ok, thank you.

ASSISTANT: Thank you and have a nice day.