I imagine the 800 minute call was started before the nightime free rates went into effect. If your free evenings start at 8pm and make a call at 7:59, the whole call is charged at the normal rate because the call originated BEFORE 8pm. It doesn't automatically change over to the free rate at 8, you would have to hang up and start the call over to get the free rate. Those ungrateful witches need to lose the phones pronto!