I called the FCC once about these types of calls and they told me the number on the caller ID is unreliable, that its easy to fake it and there is nothing they can do about it.
My home phone gets flooded with these as that’s the number I give businesses so I use my answering machine (built into my phone) to screen all those calls. So if ID says unknown and they don’t leave a message then too bad.
I also noticed that FIOS puts the caller ID messages on my TV cable display which is handy.
Yep. Despite being on the Do Not Call list I was getting a number of marketing calls from various area codes. I complained and was told it was determined these calls were being generated over a VOIP line based in Bulgaria. Out of their jurisdiction so I was out of luck.