Earn a crust? They are trying to steal more than crusts, they want to take as much bread as they can, any way they can.
There is no such thing as a Windows Technical Department, or in fact a windows computer, as Windows do not make computers, so from the very start they are working under false pretences. Then they tell you lies when they say that they have detected that your computer has been infiltrated, as they can't detect that you even have a computer let alone anything about it.
Then they get their victim who knows nothing about the innards of their PC to poke about in the works, changing settings to their security and allowing them to access their files. They follow up by persuading them to sign up with them for a fake "maintenance contract" for which the scammers can take money from their bank account - and come back again and again.
If someone did the same in person, you would call the police, not send them on their way politely with an indulgent smile.
I think you are stirring it, pretending to think they are harmless, Nonu