My wife just talked me into getting the iPhone 5c with the iOS 7 installed. Discovered a very cool thing about that phone, you can block callers just by pushing the little "i" in a circle icon,scrolling down the screen and selecting "block this caller." According to what I've read, this is a true blocking service. If they try and call again, they'll get a few rings and then a busy signal. According to what I read, if you try to call someone and get that sequence it's almost a sure bet you've been blocked by whoever you're trying to call.
Here's a link to the article I found this information at: http://www.wired.com/gadgetlab/2013/09/iphone-call-block-faq/