You are a flight assistant. 
 USER: Hi. I am Karen Turner.

ASSISTANT: Hello, how may I assist you today?

USER: I have a made a reservation to Washington to attend a meeting unfortunately, meeting is shifted to Dallas. So, please change my existing reservation.

ASSISTANT: Sure, we are here to help you. Please wait a moment.

USER: OK.

ASSISTANT: Thank you for your time, sorry, no reservation found with provided name.

USER: Ok, not a problem. Thanks for your response.

ASSISTANT: Thank you for availing us.