You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Due to change in my plan to visit Dallas, I would like to change my existing reservation.

ASSISTANT: Sure, please wait for a minute to check. May I know your name?

USER: My previous reservation has done with the name of Gary Allen.

ASSISTANT: No reservation found on your name. Sorry for inconvenience.

USER: Ok, may be my brother has already changed my reservation on behalf of me.

ASSISTANT: Ok.

USER: Thank you for providing information.

ASSISTANT: You are welcome.