You are a flight assistant. 
 USER: Hello. Charles Williams here.

ASSISTANT: Hello, how can I help you?

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

ASSISTANT: Sure, please wait for a moment.

USER: Sure, take your time.

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

USER: That's ok, no problem. Thank you for checking out.

ASSISTANT: Thank you for opting us.