Defense against a fraud company threatening to take legal action

I recieved a call from a company that form filling job should be completed within 20 days they offer 20 rs per form 1500 forms should be completed so I send them my aadhar card and they said registration is free I recieved a mail regarding terms and conditions click the link below I clicked the link it said that thank you for signing through digital signature you are bound by it then terms and conditions download Link they gave me there a clause consist of that if u don't complete ur work within 20 days u have to pay 5100+gst if u have more than 100 Mistakes u have to pay 5100 after registration they told me they'll allot tomorrow in that gap I got to know that company is fraud its main intention of 5100 rs although u completed ur work it shows more than 100 mistakes u have to pay so next day i told Iam not interested I got to know that ur company is fraud they said sir we will take legal action I said ok go on now they are blackmailing what to do?