This response is just an informative response I wrote for spam calls in general. Why the OP is getting blank calls is likely a dumb fax machine or misconfigured AI spammer.
VoIP asterisk-based AI use a call center and voice detection.
If you answer and say something you'll hear this very distinctive "chirp" followed by a human…. The system buffers calls in a tight queue and the second it triggers rings a call center monkey human to spew its BS in the sweatshop.
You can't stop this - the number called from is spoofed more than 95% of the time.
What can you do? Ignore or do this - answer on speakerphone and IMMEDIATELY go on mute. And leave it. If it's someone you know, they'll call out… otherwise they can **** off.
With my method, eventually the reports will label you as a non-working number - to like a fax or machine and delist you. If you think you can request and get a delist, you're delusional.
If you let it go to voicemail every time - that won't help you - because it's "voice" and my earlier explanation remains valid.
Reading this forum sometimes is like people that can't speak English well trying to differentiate between a "booty call" and a "butt dial".