Hi. I am William Brown.
Hello, how may I assist you today?
Owing an  emergency want to change my reservation, so can you help me with it?
Sure, I can help you best.
Thank you.
Give me a minute, I will check your reservation and get back to you.
Ok.
Thanks for waiting, we did not find any reservation on your name to change.
That's ok.
Thanks for contacting us, have a great day.