Won't discontinue my lease without a settlement payoff

i subscribed to a lease for a verifone Vx570 ITP terminal to process credit cards. It was a 48 month lease starting at $35/month, now at $42/month. I switched credit card companies and was given the option to buy the same machine for $99, which I did. Considering the outrageous cost of this machine to me over the past three years, I would expect to cancel and return theirs home at no further cost to me. They won't allow this. Should I block them from accessing my bank account?