These scumbags are spoofing Caller ID, using a VOIP robo dial program.

Sometimes, the spoofed phone numbers are not valid.
Sometimes, the spoofed phone numbers are legitimate. When this happens, the real owners of the spoofed numbers become victimized by hundreds of angry people like us.

Being on the DNC list doesn't help.
Having an unlisted number doesn't help.
A computer is doing all of the work.