You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: David Brown here.

ASSISTANT: Hello David.

USER: Due to sudden change in the event location, I would like to change my existing reservation. Can you help me?

ASSISTANT: Sure, please wait for a moment, I will check the possibility.

USER: Ok.

ASSISTANT: Sorry David, there is no reservation showing on your name, would you like to make a new booking from us?

USER: No, thanks. Thank you for the information.

ASSISTANT: Thank you for reaching us.