Company is not giving the original certificates after resignation

Respected Sirs, I was working (Dec 2011 – Aug 2012) in a company (a computer hardware training institute at Bangalore) where all employees are working in Job contract and we had to submit our Original academic certificates as a security for two years. If anyone wants to resign he or she has to give 2 months’ salary to get the original certificates back. Pathetic fact management starts torturing the employees after joining. In the contract it is written that it is the management’s right to relieve or not during the contract period. In my case I had appointed as Business Development Manager for selling training courses in colleges with 25% of travelling. But after joining travelling became 75% and more. Sometimes continuously in a stretch Kerala to Karnataka to Andhra. They asked me to visit houses also for sales of training courses. During my Kerala visit I fell down and hospitalized for 10 days. This 10 days gap they assumed that as I am going to resign. Instead of supporting my treatment, they blocked my salary. I had to get close to Rs. 15,000 travel reimbursement and Rs. 6,000 as incentives. Since these two amounts and one month salary put together it would be two months’ salary, I resigned expecting that they will return certificates. But later they did not give back certificates asking me to bring business from Kerala! I had joined that company in 2011 Dec and resigned on Aug 2012. For two years I had been asking them my certificates by sending many emails and phone calls and direct meetings. But they are not giving me back the certificates. In 2014 Aug I had approached one advocate for sending the legal notice to get my certificates. To his legal notice company replied that I had taken database from them and if I am not replying to that legal notice they will take legal action against me. My advocate told me that no need to reply for company’s reply and he will put a case against them. Soon after this my advocate hospitalized due to his illness and he could not do anything. I have all my email requests and one call recording also. What I can do to get my certificates back from this company? Kindly do reply. Just want to know these practices are allowed in India?