Company is not providing documents and asking money!!

I worked for an organisation for 3 years, and their notice period was of 2 months and they have not stated anything like "PAY IN LIEU THEREOF" for the same, when i resigned they asked/forced me to complete the two months notice period but it wasn't possible for me as the another company offering me new job was not able to extend more than 1 month. I was ready for buying my 1 month notice period too(i also have mail chains for all this) but the company was not ready to relieve me earlier. After completing 25 days of my notice period Hr sent me a mail again as reply that they will not relieve me in 1 month and i need to complete my notice of 2 months. So i decided not to continue with the company and joined another company. Now the company has sent me a notice of "UNAUTHORIZED ABSENCE" and when i asked for my relieving letter and Experience letter, they replied me with a notice that i am not eligible for the relieving and experience letter and they will recover Rs. 40,000 against not completing the notice period as Final Settlement. Now my question is Do i need to pay this amount because when i was ready to buy my one month notice period they were denying !!!? and there are cases available where they have relieved employees in less than one month. Please help if there is any option for me. As now i don't want to pay that much amount to them and they should ask for only basic salary but they are calculating with gross salary. Please help!!!!!!!!!!!!!!!!!!!