I'm sure someone else will chime in, but I use Youmail. Their visual voice mail is not free, so this may not be an option for you. I use it for call blocking, custom greetings for clients vs. friends, colleagues, etc., call forwarding, vacation minder, etc. They also offer community sharing of phone numbers (if you choose to share any) so sometimes when I get a call from "unknown", my Youmail vm will show who it was. It's a bit clunky to use when adding contacts and they do have some issues which have caused me grief, but it works well enough for now. I'm not aware of a free app that does visual voice mail for Android so, if anyone knows of one, I'd be interested in it as well.