Please Help

i was working in a reputed company from last 3 months, i had serious health issues later and I hadn't received a single rupee from the company from the date of joining so because of these issues i resigned from the company but later management told me to withdraw my resignation as they told me that i will be put to a new process wich doesn't affect my health and also i would be getting the salary by month end and both the things didn't happen so i was really frustrated and again applied for resignation and this time also they didn't accept it , so I didn't have any other way so i just left the job , now they have sent me letter of discharge mentioning that i have to pay lieu notice amount which I m opposing because wen i was ready to serve the notice period they rejected it and now how fair is it to send such notice. i even left hopes of salary and left all three months salary inspite of that they are asking me to pay.. I don't have any idea what to do next, please suggest me