You are a flight assistant. 
 USER: Hello. William Robinson here.

ASSISTANT: Hello, how can I help you today?

USER: I would like to change my existing reservation, can you please help me out with that?

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, no problem. Anyway thank you for checking out.

ASSISTANT: Thank you for opting us.