You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I would like to change my existing reservation due to my leaves got cancelled by my manager, so please help me in changing my existing reservation to Dallas.

ASSISTANT: Sure, may I know you name please for checking your reservation status in our database?

USER: My previous reservation has done with the name of Brandon Brown.

ASSISTANT: Sorry Brown, I have not found any reservation by your name in our database.

USER: Ok, not an issue. May be something went wrong while booking the ticket.

ASSISTANT: Ok, what else can I do for you?

USER: Nothing, enough with this information. Thank you for providing information.

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