Gamma LLC Refusal to return $3200 security deposit due to blatant lie about subletting New York, New York

Rented an apartment for my son and friend who were doing internships for the summer of 2012. Was required to pay all three months (June-Aug) up front along with a one-month security deposit. When he left the apartment in August, we cleaned the apartment - it was cleaner than when we moved in. One of the building staff signed a form stating that the apartment was in acceptable condition, and that we would receive our security deposit back in a few weeks. 
After one month, we had not received payment. The only contact number I had was with the building super, who referred me to "Management." The phone number he provided only led to a voicemail. I called him back and he gave me an email address. After several attempts, i finally received a reply stating that, "After review, we found that your son had illegal subleters/ renters throughout his stay.That is in violation of the Sublease that was signed. Your security deposit will not be returned to you at this time.Management."

This is an absolute lie - he never sublet the apartment during the summer. Also, legal review of lease showed that subletting was not a cause to retain the security deposit. I have had two attorneys (one in my home state, and one in NYC) attempt to contact "Gamma LLC" but they have not responded to any certified mail, etc.

I will be filing with the State Attorney's Office and will go to Small Claims Court. My son told me that other tenants in the building have had issues with security deposits.

DO NOT RENT FROM THIS COMPANY OR AT THIS BUILDING. THEY WILL RIP YOU OFF, AND THEN NEVER RESPOND.