Left the company without serving the notice period as they were ill treating me - URGENT

Could you please help me with tjis matter I have left the company where I have worked with the company for 1 year now they also started threatening saying we can get better employee on cheaper amount and started dedecuting salary aginst the policy and they also started looking for new employee. I have signed appointment letter says iI have to serve notice of 1 month and nothing is mention about compensation or in lieu. They also never sent me any letter just one call was made in which i told them since you are ill treating me i cant take this harassment , he also thretened me that he will sue me in bad case but i gave resignation and they accepted with saying serve the notice. Now they have sent me notice from advocate with aligation that i have some documents , software which are missing from office. where i have nothing and they have asked me for 3 months salary + 10K + 18%. Note they are small company never pay on time mostly post 10th - which is aginst rule and as they are 20+ employees dont pay us PF Please suggest me what i can do on it, should I revert them.. . THis is something really Urgent. Thanks,