BoostMyGrades.com boostmygrades, BoostMyGrades, boostmygrades.com BoostMyGrades actually blackmailed me. Internet

I needed some help on a calculus class.  I found boostmygrades on a google search, and decided to give it a try.  A little message popped up and asked for my information so they could give me a quote.  They told me they would just take the class for me.  I asked if this was legal and they said it was some kind of loophole.  I was in a tight spot so I decided to go for it.  As soon as I gave them my credit card things went bad.  They charged me $800, but did not keep up with the class work and I got really mad.  I threatened to do a chargeback, and thats when things got worse.
  
They told me that if I did they would go to my teacher and tell them all about how I cheated.  I was totally trapped.  They still have my money, but I finished school so I am letting the world know how horrible these guys are.