You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Can you help me to change an existing reservation with new vacation trip?

ASSISTANT: Ok, I am here to help you. May I know your name to check the previous reservation for you?

USER: Previously I reserved ticket with the name of Samantha Green.

ASSISTANT: Thanks for giving your name, please wait for a while let me check.

USER: Sure.

ASSISTANT: There is no reservation on your name.

USER: It's not a problem, I think my brother has been cancelled that reservation. Thanks for your checking and great service.

ASSISTANT: Welcome, thanks for contacting us.