Regd final salary settlement

My name is mounika , my company is asking me to pay 13000/ as final settlement for not serving the notice period, what happened is while serving notice period, i got severe medical issue, so i spoke to my TL, MANAGER, HR they told me take rest come back and serve the notice period , there will be no problem, but my surgery got delayed , due to my health condition, i was unable to report the office, i informed my tl that i just need more time as my operation delayed, will definitely come back, he didnt say anything and i got a relieving letter and mail stating that i have been charged 6000/, i didnt say that i will not serve notice period, i jst need more time. i informed the same to my TL, he told i cant do anything now, as u got relieving letter, u cant come back and serve the notice period now, i also spoke to finance department of my company, they told that it was your HR, TL mistake, we cant do anything, am not getting any help from anyone. i rely on my monthly salary, salary what i used to get is 10,000. and i dont have any job now, i cant pay this huge amount, they are also threatening me within 14 days if i dont make the payment, they will send me a legal notice. am not getting what to do. I AM HELPLESS now. my first point without even informing me they have done everything and harrasing me to pay the money. PLEASE LOOK INTO THIS. and help me