Otech — fraud and fake threat through phone calls

Dear sir,
I munnangi manjula got a call from otech company to work. It is a part time job. As i was a student, i thought of helping my family. So, i agreed to the agreement of 10000 captchas within 10 days.
After the duration of 10 days i was unable to complete the work as i have my exams.
Now, they are calling us and threatning that if we dont pay them the sum amount of 5000 they would file a case against us.
As i was unable to pay, i answered them saying it is okay to file a case on us but after like 3 to 4 months they are again calling us to threaten.
I came to know via internet about this fraud and many people like me are suffering.
I wish it would be helpful for me and to others if you can take strict actions against them.