You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I be a help for you today?

USER: Last week I have done reservation to Denver to attend client meeting there. But, due to the change of the destination of the meeting. I would like to change my reservation.

ASSISTANT: Ok, may I know on what name you have booked the previous ticket?

USER: I have booked my flight ticket in the name of Debra Clark.

ASSISTANT: Sorry to inform you that there is no reservation found on your name in our database to change the existing reservation.

USER: Ok, thank you for the information it might be cancelled by my manger but he did not informed me yet.

ASSISTANT: Thank you for approaching us. Have a great day.

USER: Thank you.