Crom Technology — asking money, multiple calls then threatening

I was registered in video watching work in crom technology.. Was looking for part time work.. I got a call that you have to apply for part time job. I said yes i want.. So they sent a link and said upload your document on it and i did it. And get my signature done as well..in a day i got they are fraud thats why i did not done the work and uninstall the app after a days, the phone calls came that you have not completed your work. You have to give its penalty, they said i have to pay 4500 rupees i got frightened then i did not pickup any calls but they started sending sms and mail with attached legal notice. They said they can settle this matter outside the court or else they will meet me in the court with indian penal court section 420 and the case is breach of contract. What should i do now.. Please help me.. They are threatening me again and again