I got an opportunity to work as an intern but unpaid.Should I join this internship?

I've recently completed my bsc in computer science and working in sales field part-time while looking for opportunities, and one day I got a call from a company(I didn't applied) in Hyderabad and they told me that they are hiring interns. They scheduled an interview for me and I went to the interview. They told after some basic questions that I'm selected even I have very little technical knowledge. Thes said that it will be an unpaid internship and if I work there for 3-4 months they will give me 1 year of experience letter but for that I have to pay them. Should I consider joining this company or just ignore it. Note: I don't want to mention the name of the company due to some personal reasons.