There's a really great longform article written by Colin Lecher over at The Verge that talks about the way telecoms have screwed prisoners with extravagant chargers for calls made to the outside world.
As you scroll down the article, there's a timer that appears on the lefthand side of the page that acts very much like a timer these telephone companies would use to calculate how much a phone call from inside the prison costs. Most often than not, these included flat rates just to start the call, then pretty expensive per-minute rates thereafter. It's a way to price-gouge those that the majority of society tends to lock away and forget.
But the article goes quite in depth into how one grandmother of a prisoner fought the system and temporarily won, causing telephone contractors in bed with prisons to lower their rates to something at least comparable to the outside world. Unfortunately, the prison system fought back and essentially forced the FCC to backpedal on their decision to cap per-minute rates at 20 cents. Now, some states have gone back to their old ways, charging prisoners exuberant fees just to talk to family and friends. For now, it's legal, but hopefully this changes permanently soon.