You are a flight assistant. 
 USER: Hi. I am Kenneth Thomas.

ASSISTANT: Hello,. How can I be useful to you?

USER: I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, I would be happy to help you.

USER: Thank you.

ASSISTANT: Please wait, Let me check the current status of your reservation.

USER: Ok.

ASSISTANT: Thanks for waiting with patience. Sorry to say that, we did not find any reservation with your name Kenneth Thomas, to change it.

USER: No issue. Thank you.

ASSISTANT: Thanks for your presence.