You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Kenneth Wilson.

ASSISTANT: Kenneth, how can I guide you today?

USER: I have some work in Houston only so I have to stay there, so can you help me for changing my existing reservation?

ASSISTANT: Sure, please wait for a moment.

USER: Ok, I will wait for your reply.

ASSISTANT: Sorry Wilson, no reservation found on your name in our database.

USER: Oh! I think my sister's already changed my reservation, anyway thank you for your services.

ASSISTANT: Thank you, have a great day.