You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Larry Brown here.

ASSISTANT: How can I assist you?

USER: I want to change my existing reservation, due to heavy rains. Can you please help me?

ASSISTANT: Sure, I am here to help you to change your existing reservation. Give me a moment.

USER: Ok, take your time.

ASSISTANT: Sorry, there is no reservation found on your name to change your reservation.

USER: That' s ok, thank you for checking.

ASSISTANT: Welcome. Thank you for checking.