My phone number has a VOIP number in which the primary Sprint number was owned by someone else and they had numerous collection issues.
Here's what I did:
If you have an Android phone, then assign the caller name DNA1, for Do Not Answer, 1 being the first, etc. Once you have created the Contact, go to Options and select Send call directly to voicemail.
I have over 50 DNA's on the phone but live in peace...
nope, who wants to have a bunch of spammers in voicemail? no one! The right answer is to get a blocking app and keep those two-legged garbage from ever bothering one or even connecting to voicemail.