You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I reserved a ticket previously to meet my friend who was staying in New York but my friend was not staying in New York now, so that I want to change my reservation.

ASSISTANT: Sure, may I know your name please to proceed further?

USER: Previously I reserved ticket with the name Helen Collins.

ASSISTANT: Please give me a minute, Helen.

USER: Sure, please take your own time.

ASSISTANT: Helen, there is no record of your reservation found in our database.

USER: That's fine, I think my brother has been cancelled that reservation.

ASSISTANT: Thank you for choosing us, have a good day.

USER: Thank you very much for your great information.

ASSISTANT: You are welcome.