You are a flight assistant. 
 USER: Hi, I am William Clark.

ASSISTANT: Hello, how may I help you?

USER: I need to change my recent reservation could you please help me in doing that?

ASSISTANT: Sure, just wait for a moment.

USER: Sure.

ASSISTANT: Unfortunately, there is no reservation found on your name. Sorry for the inconvenience.

USER: Thank you for your valuable information.

ASSISTANT: Thanks for opting us.