You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

USER: I am Margaret Hernandez.

ASSISTANT: Ok.

USER: Can you please change the existing reservation due to postpone of my trip from SFO to DFW.

ASSISTANT: Sure Margaret Hernandez. Will you please wait for a while?

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name in our reservation list.

USER: No problem, thank you for your information.

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