Quit the job without serving notice period

Hii, I was working with Delhi Public School Jaipur, I resigned there without serving notice period as I was facing mental harassment from last one year. I got an offer and discussed with hr for the resignation in july 20, 2021 but she told me not to put the resignation on papers talk verbally with Principal, it was a verbal discussion after one week of discussion I got ill and took 2 days leave now they thought I have left and they hold my salary of july. I got yo know when everyone receives except me. They made a cheque for me,, then they started harassing me on leave matters and other issues, principal was like speaking anything in front of others.one day I decided to resign because I was not able to make up my mind to go there, I was so much depressed, I was taking care of the 3 employees work since march 2021, still she used to say kya karti ho tum , now they are giving me threats by mail to serve notice period or amount in lieu of that.they have slready relieved my employee in the notice of just 15 days and didnt ask for amount. But they are harassing me sending emails.