Threat call from Kotak bank recovery agent

Hi, I had Kotak bank Credit card at 2011 with some outstanding as I lost my job. Now after 4 years they approached me and asked for payment. I asked then I can do account settle but in the month of January. On this account I had marked mail to banking ombudsman and got the revert on same. Last week this person seen his executive at my home and make harassment. Now today at 8:29pm he called and asked for payment of 15000 settlement amount. I requested him that I have not arranged funds, and I had also requested banking ombudsman for providing time. He started abusing and treating for sending recovery agent at my home and all. I called customer care and raised complaint for harassment. I had all recording of today call. Please suggest where I can approach for this... Please....