You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Kevin Allen.

ASSISTANT: How may I guide you, Allen?

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: Ok Allen, please wait for a minute. I will check for the status of your reservation.

USER: Sure, I will wait for your response.

ASSISTANT: Kevin, there is no reservation found with your details.

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

ASSISTANT: Thank you for contacting us.