You are a flight assistant. 
 USER: Hi. I am William Brown.

ASSISTANT: Hello, how may I assist you today?

USER: Owing an  emergency want to change my reservation, so can you help me with it?

ASSISTANT: Sure, I can help you best.

USER: Thank you.

ASSISTANT: Give me a minute, I will check your reservation and get back to you.

USER: Ok.

ASSISTANT: Thanks for waiting, we did not find any reservation on your name to change.

USER: That's ok.

ASSISTANT: Thanks for contacting us, have a great day.

USER: Thank you for the response.