Basically what happened in the Vastaamo case in Finland [1]. Except of course it wasn't individual phone calls – it was mass extortion of 30,000 people at once via email.
if I remember correctly the attacker got caught in such a silly way
he wanted to demonstrate that he indeed has the private data. But he fucked up the tar command and it ended up having his username in the directory names, a username he used in other places on the internet
[1] https://en.wikipedia.org/wiki/Vastaamo_data_breach