Both of my Motorola phones (V600, V635) give the normal ring to Unknown Caller. Solution? Make your normal ringtone what you want it to ring for "Unavailible", then make a contact group (you might want to grab the Motorola OS [from the Alltel firmware] and ditch the crappy Verizon one) with everyone whom you want to have what would be your normal ringtone. Then customize ringers as you normally would.