Zylon Services — Blackmailing

I have applied for part time job on quikr then within two days I get a text msg from a company name zylon services the Job was of captcha filling thn they send agreement n thn called for verification all was done when did they started work I wasnt knowing then after some days the work wasn't completing then I email them to cancel they refuse and demand for penalty 6900 and 2500 charge then they were threatening and harassing me saying they will take legal action