I've paid money because of a fake agreement with REX ENTERPRISE, so I

I've joined a part time job in Rex enterprises and they have made an agreement. And as per the agreement if the work is not correct I've to pay Rs.I've paid I've paid it too. After that a man from REX ENTERPRISE called me and asked whether you are willing to continue the agreement or not. I told him to cancel the agreement but for that they are demanding more money from me. That is to cancel the agreement, I've to pay Rs.12000 or else your case will be filled in the court. I got doubt because this was not mentioned in the agreement. So when I was checking in the internet I got many cases like mine. And even the serial number is same for all. So I request you to enforce law against 'REX ENTERPRISE' and refund my money(Rs.4300)