Met Tech — fraud call and harassment

This company has given me online form filling work. They provides other countries data which is impossible to complete with in 15 days so I said them to quit the agreement then the call and harass me and saying I have to pay 7800. Now one person is calling me and send me a fake legal notice which is saying that I have to pay 5500+4010. There are lots of complaints of this company. This company is doing same for all. Please help me.