NOTICE PERIOD

HELLO,
I JOINED A LOCAL COMPANY IN AUGUST 2015 AS AN ACCOUNTS EXECUTIVE. THEY ISSUED ME AN APPOINTMENT LETTER BUT IN THAT LETTER THEY DID NOT MENTION ANY NOTICE PERIOD. HOWEVER, WHEN i GOT NEW JOB, I DID GAVE THEM PROPER NOTICE PERIOD. i WAITED IF THEY WOULD APPOINT SOMEONE SO I COULD HANDOVER ALL MY FILES AND WORK TO HIM/HER. BUT THE THING IS THEY DID NOT HIRE ANYONE DURING THAT NOTICE PERIOD. AFTER COMPLETION MY NOTICE PERIOD,I LEFT THEM AS I DID NOT KNOW TO WHOM I SHOULD HAND OVER(THEY ARE TYPICALLY SETHIYA COMPANY AND THEY DO NOT KNOW EVEN A WORD ABOUT ADMIN,ACCOUNTS AND HR.)
NOW THEY ARE THREATENING ME ,WHEN I TOLD THEM I WAS NOT BOUND LEGALLY TO SERVE NOTICE PERIOD BUT I DID SERVE THAT PERIOD NOW THEY ARE SAYING I CHEAT THEM AND I DID WRONG TO THEM.I DID NOT CHEAT THEM. I DID NOT TOOK EVEN A SINGLE PENNY EXCEPT MY SALARY. ONE MORE THING I WAS THE ONLY ONE IN ACCOUNTS DEPARTMENT AND I THINK FOR ME IN THIS SITUATION IS REALLY DIFFICULT TO PROVE MY INDECENCY. WHAT CAN I DO NOW, THEY ARE THREATNING ME THAT THEY ARE GOING TO ISSUE ANY LEGAL NOTICE PLUS REGISTER FIR AGAINST ME.