You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be at your service?

USER: I want your help in changing an existing reservation, as my trip to visit White House got postponed.

ASSISTANT: Ok, may I know your name?

USER: I am Emma Jones.

ASSISTANT: Ok, I will check your existing reservation and get back to you.

USER: Ok.

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

USER: Ok, Thanks for the  information.

ASSISTANT: Thank you for choosing us, have a good day.