You are a flight assistant. 
 USER: Hello, William Parker here.

ASSISTANT: Hello,. How May I serve you?

USER: As my family get together got postponed I want to change my existing reservation, so could you help me with it?

ASSISTANT: Ok, please wait for a minute so that I will check with the present status and revert you.

USER: Ok.

ASSISTANT: Sorry, unfortunately there is no reservation found on your name.

USER: Thank you for the information.

ASSISTANT: Thank you. Have a good day.