Agreement issue

I had started working for a online company .They took my signature's to a online agreement.until I realized it it was to late And in that agreement condition was this that I have to complete 10000 Captcha with 90% accuracy that I can make only 1000 mistakes otherwise I have to 5000 as penalty amount and ..I thought that i was able to do this it wasn't that easy... then when I started working their app was not working properly for the first three days and in between the days I even sent a gmail to them that how to get out of your agreement they said just pay the penalty amount that time I don't have any else option rather than doing my work I started doing again... and I realized that amount of work was very big some how I did complete 4000 something captcha within 10 days and the 1000 mistakes were also completed... now they are texting me that my work is not complete and I have to pay the amount now I don't even know it was a fake company or not I can't pay this huge amount ...I did a stupid thing before... I don't want to do more so please help me out sir