Because Verizon is one of the worst carriers in detecting spoof numbers. Everything was supposed to change on June 30th and the FCC gave the telecoms the ability to auto-block calls that were from spoof numbers from spammers but nothing has changed at Verizon. I get 8-10 calls a day from the Social Security Administration, Amazon, the Federal Reserve, Auto Warranty Companies, Directv, all scammers and all using phony numbers. There are countless small offices of scammers with a windows computer somewhere in Nigeria, Jamaica or India and they are outsmarting Verizon's network operators. It is too bad these scammers don't operate a wireless network, I bet they could figure it out.