No appointment letter served and harrasment by employer

I have not served any offer letter or appointment letter or any thing in which there may be mentioned of the condition of 1 month salary or 1 month notice period to be serve after giving resignation but still my employer is demanding my 1 month salary or to serve 1 month notice period Today he tried to threat me on phone , he used the word" main north india ka goonda hoon, mujhe koi chutia nahin bana sakta, main tujhe saturday tak ka time de raha hoon nahin toh iske baad jo kuch bhi hoga uski jimmedari meri nahin, apan police police baad mein khelte rahenge, main 25000 k liye 25lac bhi karcha kar sakta hoon , tere toh main 2.5 cr lagwa doonga, ye ab mere ego pe aa gayi hai". Please suggest what should i do or keep calm and let him do what he could!