The phone companies won't allow whitelists because this will cut down their income. The current arrangement allows the phone companies to sell phone lines to telemarketers and scammers and then sell you defensive options like CallerID to fight them. It's like selling weapons to both sides in a war. Phone companies make money while you and I suffer.

I get this one too.  Again, I am convinced they use numbers in order to get past call blockers.  It is sad that the phone company doesn't let you block all numbers except those on your list.  That would shut these a____holes down