This is a well known scam that has been going on for years in various guises. They may claim to be from "The Windows Department", Telstra or other big companies to do with computers and telecommunications. Mostly they know nothing about you, their system dials numbers at random or from a phone book trying to get a human to answer.
Typically they seem to be from Philippine or Indian call centres. It may be tempting to pity them and to see them as the poor downtrodden who have little choice in the work they do. I don't. They know they are lying and cheating people and keep doing it year after year so all civility and humanity is off from me.
They are after your personal details, which may lead to identity theft, or to get you to allow them to control your computer remotely for nefarious reasons, or both. Under no circumstances allow them to download or install anything on your computer.
Unless you want to play with them (and be foully abused when they twig) hang up quickly.