You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: Can you please help me in changing my reservation?

ASSISTANT: Sure, can I know your name?

USER: I am Charles Johnson.

ASSISTANT: Please wait a moment, let me check your details.

USER: Ok.

ASSISTANT: Sorry, there are no active reservations on your given name to change.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching our service.