You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I had a done a wrong estimation of completion of my work. So, I would like to change my existing reservation. Can you help me?

ASSISTANT: Sure, I will help you. May I know your name please for checking your reservation status?

USER: Sure, my name is Thomas Baker.

ASSISTANT: Ok, please hold on a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation has been found on your name.

USER: I guess I have changed it before. Anyways, thank you for the information.

ASSISTANT: Thank you for choosing our service.