The problem is either caused by password traders or chargebacks due to insufficient satisfaction, as I see your sites have an oldschool cookie cutter design and thus might only provide matching content that few people want to pay for these days.
The best way to lower fraud is webmaster monitoring and automated phone number verification.
http://www.phoneconfirm.com/
http://www.proveout.com/
http://www.verexo.com/
etc.