You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I 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: May I know your name to change your existing reservation?

USER: My previous reservation has done with my name Ashley Garcia.

ASSISTANT: Sorry Garcia, no reservation found 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 contacting us.