You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Stephen Smith here.

ASSISTANT: How may I assist you at this moment?

USER: Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, I will help you with that.

USER: Thanks.

ASSISTANT: Please be on hold to check your previous reservation.

USER: Ok, I will wait.

ASSISTANT: We regret to inform you that, there is no reservation found on your name in our records.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for reaching us, have a great day.