An online game, Eve Online, let's you set a fee for anyone not in your contacts to message you, with a default fee. You get some of it and "the government" (the game) gets the rest. The first time you message someone, you get prompted to pay the fee or discard your message.

I want this in real life. Set a default of a $1 or so. Your carrier gets $0.25, you get $0.75. You can adjust the fee to $0 or $1000. Carrier gets 25%.