You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want change my existing reservation, can you please help me with this?

ASSISTANT: Sure, please share your good name?

USER: Robert Johnson here.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your given name.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.