Harrasment against the serco bpo

complaint of Harrasment against the Serco Bpo Delhi. I have contacted the office both by phone and in person and have received no response. Most recently, I have also sent a Legal Notice to them for non payment of dues on 20/06/2013 but till date I have not received any reply from them. Most recently, on Febuary 13 2013 , I had given my resignation to the company in person to the Manager after which I was relieved from my duties, pls suggest remedy to take f & f with experience letter