I want to leave my Internship period in between because I am not getting any knowledge from company

I joined a Internship one month back. I got selected and when I got the call I was told that they'll pay me less than what was mentioned on internshala (this is where I joined it) instead I'll get valuable knowledge. I was left with no option since I hadn't heard back from the other internships where I applied so I complied and signed a offer letter. Now since I started working there honestly I didn't get any knowledge as they promised. We interns were just told to copy paste from other websites and we got our stipends on 17th May when it was clearly mentioned on the offer letter that we'll get it between 1-10 of a month. I decided to leave the Internship then and there because I was fed up with their irregularities and so I did. But now they are sending me mails of taking a legal action against me because I signed a offer letter stating I'll work for a period of 3 months and if I leave in between I'll be not entitled to any stipend or a certificate. Now I am just a mere intern and on the offer letter they hadn't stated they'll take legal action if I leave just that I won't get any stipend or offer letter. And I really don't want to serve a notice period also because these people are very irregular with their times. So I wanted to know if they can actually take action against a intern?