You are a flight assistant. 
 ASSISTANT: Hello, how may I help you?

USER: Hello, I am Charles Walker. Can you please help me out in change my existing reservation?

ASSISTANT: Sure, I am here to help you. Please wait a moment.I will check and revert you.

USER: OK.

ASSISTANT: Thanks for waiting. Sorry there is no reservation found on your name.

USER: Thanks for the information.

ASSISTANT: Thanks for connecting us, have a great day.