I already have a /dev/null contact with a silent ringer but the telemarketers (especially the neighbor dialing) almost never uses the same number twice. Still hopeful the ATT app helps though.
Their list automatically updates based on whatever mysterious processes happen in their end, so it should be an improvement over manually blocking numbers after you get a spam call. Hopefully it will help a little bit. It's definitely not a cure, but we have to take what we can.