Gave me Fraud Legal Notice

I joined one company with interview procedure there were lot of students came for interview and company demanded bond amount company said they will return bond amount after 6 month.hence I gave them 20000 before joining there were lot of things they did not tell to joiners there were approx 50+ frashers in that company all did 20000 payment to that company.1st day in company they say you will have to do training first for first 15 days after that you will have to undergo for test.this was not told us before joining.i searched about the company then I found company to hire and fire policy to collect bond amongst from frashers.i even do not know about the CEO of company and hr do not give details about him. After company status I decided to look into other opportunity and I left the company within 15 days.i tried to get my amount but they sent me legal notice where they said we are genuine company and you are spreading wrong things about the company then I found bad reviews about the company In different platforms.Now I have legal notice sent by the company they are claiming that you have stolen our client data from server but I even did not worked upon there and not did even one project and they want 500000 from me I think the same notice is sent to everyone who were working there. We are frashers came recently into the profession please help to come out of there