You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. In which way I can aid you today?

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: Sure, I can help you with that. May I know your name for further process?

USER: My previous reservation has done with the name Frank Harris.

ASSISTANT: Ok, please hold on a moment, I will check your reservation status.

USER: Sure, take your own time.

ASSISTANT: There is no previous reservation in your name Frank Harris.

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

ASSISTANT: You are welcome.