Pro Techno — harassing emails and calls

I'm the victim of pro techno form filling job. They gave me 800 pages of data and complete it by 7 days the registration fee is 4100. But i didn't submit the work. After one week i received a mail from mayurjoshi an advocate addressing that i need to pay 8250. If not means a legal notice will send to the given address. They are threatening me. Pls anyone help me. How should i come out of this mental stress. Daily they are calling me. Help me frds