It's explained on the site somewhere I think but when you click to send you have to tick a box that says you have turned off your pop-up blocker, (of-course you don't actually have to), but when you do a pop-up comes up at the end, so I think thats were the money is. Oh and when somebody text's back they get some of the 15p it costs to send a text I believe, Thats why they want the recipient to text back.