You'd think the ability to block calls from certain numbers would be built in to most phones by now, but that's certainly not the case with the iPhone.
After dropping a few hundred bucks on a device, it'd be nice to be able to choose who you want to talk to, but beyond screening calls, there's no simple way to keep unwanted numbers from getting through.
Call Blocking in iOS 7
iOS 7 does have a new feature that allows you to block numbers on your iPhone, but rather than a true block, it sends them straight to voicemail.
Real Call Blocking in iOS 7, iOS 6, & Earlier
There's always... more