Uc Solution — blackmailing for paying money

Few days back i got a message from uc sollution regarding part time online form filling work (Home based), and the told me that there is no registration fee required fir this, so i got attracted towards the job and applied for it. For this they asked me for uploading my adhaar details and i did the same, and made me signed the agreement online.
They said to complete the work in 10 days but after some days when i search for the company online i found many complains regarding the company and i started feeling unsecure and didn't continue the work.
Then 10 days later i got a call from the company to pay the amount of 7500rs for nit completing the work, but this was nit told earlier. When i didn't pay the amount a day later i start getting a call from a person claiming himself an advocate and blackmailing me to pay the 7500rs to the company or he will issue a legal notice against me, so i stop receiving the calls from them.
And today when they called me again and i didn't recieve so the send me a text message that the legal notice has been issue.

Please sir help me tell me what to do..