You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: My name is William Clark and I want to change my reservation. Can you please help me?

ASSISTANT: Ok, I will help you with that. Please wait for a while, I can check and let you know about your reservation status.

USER: Take your time.

ASSISTANT: I regret to say this, there is no active reservation with your name to change the reservation.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for reaching us.