You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I have postponed my trip to Dallas. Can you please help me by changing the existing reservation?

ASSISTANT: I am here to help you, can you please provide me your name?

USER: My previous reservation has done with the name Andrew Lewis.

ASSISTANT: Lewis, I will check your reservation details and get back to you. Sorry Lewis, I have not found any reservation by your name.

USER: Ok, not an issue. May be something went wrong while booking the ticket. Thank you for providing information.

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