You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: I want to change my existing reservation due to sudden postpone of  my trip to San Francisco. Can you help me with that?

ASSISTANT: Sure, may I know your name?

USER: I am Larry Hernandez.

ASSISTANT: Please wait a moment.

USER: Sure.

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

USER: Ok, no issues.

ASSISTANT: Thank you.

USER: Thank you for your response.