How do I delete a program called "Movieland" which somehow got on my computer?

I tried everything but it keeps on sending pop-ups that cover my entire screen and demanding money or I can’t use my computer. It claims that I went beyond my 3 day free trial, which I didn’t order, and now I must pay a month or I can’t use my computer. Is there an agency or legal thing that I can do about this? I need help fast because this is on my computer at a cancer clinic that I run and all the patients’ files are on it. And I can’t get to them. Help! I even tried calling the company but that didn’t work.