Regarding illegal bond

Hi, I am working in a private software company as an software engineer. I am working in the same company since last 3 years. one day my HR come with a bond letter on a normal paper which dint had any stamp and neither it was company letterhead it was a normal A4 size paper. On that paper it was written that they will provide training of 3 lacks so i have to sign that bond immediately. he takes my signature forcefully on that paper although i ma trained in all technology that they are providing me training. after few months they dint conducted any single session of the training and told me that your training is over and i have trained you whatever you know till now so if you try to leave our company you need to pay complete bond amount. Even after this they are not providing salary increment and not accepting my resignation. and now they have started harassing me mentally. no one is there to talk with and can listen our complaint inside the company. all are same including company director, Team lead, HR, project manager everyone are on same side. so what should i do now to get out of these.