Dgs Sol — i have not completed the work with in time, they are asking 10, 580/- to extend the time, otherwise they said that will send the legal notice

Sir, i am a student. I saw a advertisement in quikr job site, applied for typing work.
They asked me to complete 800 forms in 8 days, due to my exams i couldn't complete the work with in time. Today they called me said to pay some amount for not completing the work. They demanded 10, 580 rupees to be paid for extension time and said if you want to quit, you need to pay 13, 588/- otherwise will send legal notice.
Sir please give me solution... I don't have that much money