I'm getting emailed fake invoices from "Microsoft" for Windows Defender about once a week.

Instead of using attachments, or websites, it just has phone number I'm supposed to call. It usually asks for about $200.

In my cases, the phone number appear to be in the US.

It may fool businesses more than individuals, because many vulnerable people wouldn't know how to call an international number.

I think the scammers keep the amount small so once they identify you as a sucker, they can put you on a suckers' lists, and resell it.

US telecom provides don't seem very interested in preventing abuse, even when their laws to implement a bar minimum law, around robocalls.

Massachusetts UR state news, MassLive: Only a fraction of phone providers have complied with new robocall regulations

A Sept. 28 deadline is meant to better protect consumers from robocalls scams that steal more than $10 billion annually. However, new data shows that only a fraction of phone providers are prepared for Tuesday’s deadline.

...“How much longer are we going to tolerate people’s lives being destroyed when they fall for an imposter call that looks like it’s coming from their bank or the IRS? This is inexcusable, it has to stop, and phone company compliance will make a big difference,” Consumer Program Director for the MASSPIRG Education Fund Deirdre Cummings said. “Phone companies have known about this deadline for five years. The FCC told companies to do this three years ago and Congress passed a law mandating it nearly two years ago.”

...In Massachusetts, residents received on average 75 robocalls per person, a jump of 29% from 2018. In December, 48.7 million robocalls were made to Massachusetts residents alone, averaging out at 1.6 million calls per day and 5.9 calls per person.

Illegal robocalls lead to $10 billion a year in fraud, according to the Federal Trade Commission. The calls cost consumers an additional $3 billion a year in wasted time, according to the FCC.