Ultimate Readers' Service Bait and Switch, Won't cancel subscription Lakewood, Ohio

I signed up with Ultimate Readers' Service because it seemed reasonable.  Shortly after I started rec'ing magazines, I rec'd a call from a rep advising the price was going up.  I told her that I agreed to pay a specific price and I should be grandfathered in until the agreement expires.  She insisted I would have to pay a higher subscription fee, so I told her to cancel the service.  I have since rec'd calls from other reps and a manger asking for payment.  I told them I feel the service pulled a con called "bait and switch."  They got me to sign up for one price, then switched it to a higher fee.  I have, each time they called, told them to cancel the service.  They have sent me a letter stating "we" reached an agreement and "we" could work out a payment schedule.  "We" did not reach an agreement and I refuse to pay for a service which I cancelled.  The problem is with the Ultimate Readers' Service:  they refuse to cancel my subscription even though they have been told to do so several times...and they continue to send me bills.  I want them to stop billing me for a service that I have cancelled.