You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Due to change in my plans to visit Dallas, I would like to change my existing reservation. Can you help me with this?

ASSISTANT: May I know your name please to check your reservation status?

USER: My name is Charles Thompson.

ASSISTANT: Charles, no reservation has been found on 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.