Get yourself a standalone digital answering machine.
Our home phone has had various answering machines fire walling since I can't remember when.
Nothing gets through unless it is both important to us and the caller.
As most calls are computer generated, they usually drop out very quickly and we get a short busy tone msg that is easily deleted.
Our regulars know the deal and warble on till we pick up or leave a message.
No costs to call the voicemail.
I have been thinking for some time to buy a few units and put away in case they are no longer manufactured.
We are not on the No Call Register and never will be.
Life is good this side of our firewall.