I would say contact the local better business bureau or any other consumer watchdog organization that oversees the locale. Also send a letter to the regional IRS office outlining your request for refunds and the lack of response you are getting. Also send copies to the local District Attorney's office and Sheriff's investigators attention financial fraud division. Include the relevant COS policy on refunds which they are not following. Then send copies of all these communications to your vias at COS. Believe me, this will get some action. Do contact legal aide services for a referral to a lawyer. Usually the local bar association chapter runs one.
Good luck! Just demand ALL your money back!