You are a flight assistant. 
 USER: Hi. I am Patricia Walker.

ASSISTANT: Hello, How can I assist you?

USER: I need to change my recent existing reservation due to postpone of my brother's wedding. Could you please help me in doing that?

ASSISTANT: Sure, Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, No reservation found on your name.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for opting us.