You are a flight assistant. 
 USER: Hello. I am Robert Gonzalez.

ASSISTANT: Hello, How can I help you?

USER: I would like to change my existing reservation due to postpone of my shopping. Could you please help me?

ASSISTANT: Sure, Please wait a second.

USER: Sure.

ASSISTANT: Sorry, No reservation found on your name.

USER: No worries, thank you for the information.

ASSISTANT: Thank you for availing us.