Deltatech Data Solutions — regarding fraud and demanding for money

So i got a call from deltatech data solutions, they asked me for a home job and asked me to fill 800 forms in 7 days time. I complete my work before the time period given. After that i tried calling the executive for continuously 3 days and she doesn't replied. After which i got a call today from another girl asking me to pay 4000 before and threating me for legal notice. I said the other executive earlier that i will not pay a single penny after my work is completed. Even i asked them to give me the details of the wrong forms submitted but she is talking rudely and is asking continuous for money. How someone can do this. It's a form of harrassing the candidate and before joining this i even asked her about the complains and etc. This company need a strict action on them or else they will do the same with all