You are a flight assistant. 
 USER: Hi, I am Dorothy Nelson.

ASSISTANT: Hello, how can I be of your help?

USER: I want to change an existing reservation due to my seminar got post pone.

ASSISTANT: Ok. Please wait a while. Let me check and revert you.

USER: Ok.

ASSISTANT: Thanks for your time. Unfortunately there is no reservation found with your details.

USER: Thank you.

ASSISTANT: Thank you and have a nice day.