You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

USER: Jack Clark here. I was made a reservation earlier in this week. But I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, I am happy to help you with that.

USER: Ok.

ASSISTANT: Please wait a moment and I will check your reservation status.

USER: Ok, I will wait.

ASSISTANT: Sorry Jack Clark, no reservation has found under your name to change.

USER: Anyway, thank you for the information.

ASSISTANT: My pleasure. Thank you for choosing us, have a great day.