You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist 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, can I know your good name please for further process?

USER: My previous reservation has done with the name Deborah Miller.

ASSISTANT: Ok, please stand by. There is no existing reservation find on your name in our records.

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

ASSISTANT: Thank you for approaching us.

USER: Thank you for providing information.