Is there a way to block spam calls automatically from a know list of known callers?

Up until this week, there was a way; I was proceeding to block up to a maximum of 100 "unavailable" callers.  Suddenly, I find that's not available at all.

Now *77 is supposed to stop the anonymous calls, but does that do anything to get rid of the "unavailable" callers?  I receive up to 25 of these per day.

Robert ( Edited as per the community guidelines )

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@Robe54 The answer given 5 months ago is correct. Unavailable/Private/Anonymous calls are from someone wishing to block their outgoing caller ID, which *77 should block, or simply don't answer them. Unknown calls are calls where no information was sent, which can't be blocked by the phone companies current blocking methods, because there's no information to block. As stated 5 months ago some phones or third-party blocking devices can block them.  

Yes, you can block spam calls automatically from a known list of callers by using call-blocking apps or features available on some smartphones. Add the known callers to the blocked list, and the app/feature will prevent spam calls from those numbers.

This topic is not about cell service.