Northern Leasing Systems, Inc. Wants Settlement to discontinue $42/mo lease for a $99 product. Have already paid approx $1200 for this product. New York, New York

My credit card processing company, Transfirst in Colorado, called me in June 2009 to tell me that my current processing terminal was outdated and that I need to update to a current terminal to prevent hacking. By law, they said.  They offered me a monthly lease for a terminal that they said cost over $2000. I signed up for a 48 month lease at $34.98/month (the rate has increased to $42/month since then).  Recently, I switched to anopther credit card processing company because of my outrageous rate of Transfirst. The new company offered me the SAME terminal for a total cost of $99.  When I called Northern Leasing to send the terminal back and discontinue the lease, they wouldn't budge, stating I had nine months left and must pay a settlement of $310. Crazy.  How do I stop them from ripping me off more than they already have?