You are a flight assistant. 
 USER: Hello, I am William Garcia.

ASSISTANT: Hello, how may I assist you?

USER: I want to change my existing reservation due to change in my travelling schedule. Could you please help me?

ASSISTANT: Ok. I will help you, please wait a minute.

USER: Ok.

ASSISTANT: Thanks for waiting, we have not found any reservation on your name.

USER: That's fine, thank you for the information.

ASSISTANT: Thank you for reaching us.