You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, How can I assist you?

USER: I am Samuel and I want to change my existing reservation.

ASSISTANT: OK, Please wait for a moment I will check and get back to you.

USER: Sure.

ASSISTANT: Thank you for waiting. We do not find an flight based on your details.

USER: OK, Thank you.

ASSISTANT: Thank you for choosing us.