You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you today?

USER: I am William Thomas. I would like to change my existing reservation, due to heavy rains. Can you please help me?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait a minute.

USER: Sure, I will wait for your response.

ASSISTANT: We are regret to inform you that there is no active reservation on your name to change.

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

ASSISTANT: Thank you for choosing us.