Legality of Service Bond without Appointment letter signed

I was working as a software developer trainee in IT company. I signed service bond (only 5 lines on 100rs stamp paper) stated that If I leave the company within 2 years from the date xx-xx-2016 I have to give them 1,00,000rs. But they didn't issued any appointment letter that explains my role, salary, training, resign procedure etc.. They were providing me only 6000rs salary every month to bank account. I worked there for 5 months, they started telling me that I am not worth for 6000rs, that hurts me very much I left the company by sending resignation through email with good review only without stating any bad remarks. Now they are sending me legal notice through lawyer to pay compensation amount (service bond amount) of 1,00,000. 1. Only Service Bond signed on 100rs stamp paper (only 5 lines of statement) 2. No appointment letter given 3. Only 6000rs per month salary to bank account no pf nothing. 4. They orally said after 3 months they will increase my salary to 12000rs, so I signed bond. 5. I was from distant place, I stayed there in PG. 6000rs per month very difficult for living that too 2 years. What I should do now? I don't have money to spend on lawyer. Can I neglect the lawyer notice?