Didn't got salary and original certificates after resigning

I'm from Mangalore, currently working in Bangalore. I'm BE graduate. I joined one private non destructive testing company on February 2016. After joining they made me work like a dog. 2 and half month completely sent me for night shift. Its not normal night work, its radiography testing open field site work. We need to move to customer site and have to work. I exposed to over the limit of radiation due to continues night work. Still no one bothering about us. But I had never mind that I'm a BE graduate. After getting experience of 6 month we can write BARC level 1 examination. For that they taken our originals at the beginning itself. There is no bond system in the company its very clear. End of 4 month my health was not good so I decided to give resign. Now they are refusing to give my last month salary and all original documents from SSLC to BE. There is no bond in the company,no appointment letter,not provided company employe I'd and account.They also made problem in payment of night shift OT. Pls sir I need your suggestions.