Company denying for relieving letter

Dear Sir, I worked in a healthcare firm in New Delhi for 2 years 9 months. I resigned from there on 10th January 2015 and served notice period till 25th March 2015. (Company notice period is 2 months). Handed over each and everything to the concerned persons, but they denied to give acknowledgement or acceptance. In April 2015, I joined MNC in gurgaon after signing a undertaking that I'll submit my relieving letter within 2 months of my employment. I failed in submitting relieving letter and they terminated me in September 2015. For my due salary and relieving letter, I filled a case in concerned labour office. It's been more than 3.5 months company has not given relieving letter and salary. Labour court has sent more than 3 notices to the management for relieving letter and due salary, but they are not replying. Can I furnish notices which have sent to the management by saying that management is not giving relieving letter? Is there any law by which I can defend myself for not having relieving letter.