American Express India — Inappropriate charges on credit card and harassment for the same

It is more than 6 months I have closed my card and reason for closure was inappropriate late fees and finance charges that were under dispute. The company delayed a lot to reverse the charges and kept on applying late fees and finance charges on my card. I wrote multiple emails to them and sought revert but it was unanswered. Suddenly company is sending collection agents to my residence and asking for payment that is not due. I have explained and provided break up of payment made by me. This is not solved even after escalating it to Nodal officer.