Datalink Infotype — making calls n threatening me to pay the penalties...

Hi, recently i took work from datalink infotype as im looking for online jobs. They informed me to complete 2200 forms in 20 days and if i failed i have to pay penalty amount. After seeing all the complaints against them i realized it is a fake company and i stopped working. I even told the person to cancel my id from whom i received the work. There is no response from him and now they are sending legal notice to my mail. They are threatening me to pay the amount otherwise case will be filed. I dont know what to do. I dont want to get into any legal kind of things. Please help me out from this issue. Thanks.