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, I can help you in changing your reservation. Can you please let me know your name? So that I will check your reservation status and let you know.

USER: My previous reservation has done with the name Carol Thompson.

ASSISTANT: Carol, let me check your reservation status.

USER: Sure, take your own time.

ASSISTANT: Carol, I have not found any reservation by your name in our database.

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

ASSISTANT: Thank you very much for contacting us and have a great day.