You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Dennis Smith here.

ASSISTANT: How may I guide you today?

USER: Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

ASSISTANT: Sure, I will help you with that.

USER: Ok.

ASSISTANT: Please wait for a while.

USER: Ok, I will wait.

ASSISTANT: I am sorry to say that there is no reservation found.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for contacting us.