I had a really nice detailed post but it looks like it didn't submit
So to be short and sweet (ask if you want details again), you can do any of the following:
1. Buy either of those apps

2. Change your voicemail to first have a fax machine beep or one of those "I'm sorry, the number you have dialed has been disconnected" or a busy signal for about 10 seconds. This wards off spam callers and they put down the line's dead

3. If it's your Google Voice (GV) number, look at GV's new feature to have your phone not receive calls from the user-created spam call database
4. Port your phone# to GV for a one-time $10 if it's your actual cell phone # having the issues. Make sure you only do this out of contract so it doesn't terminate early!
5. Add those #s to your "block caller" list on your phone. I believe this is a native Android feature, or at least on the phones I've had.
I had much more details but will only post them if you find this relevant lol! Best of luck, friend