Security Networks Will not let me cancel after being with company for 4 years West Palm Beach, Florida

I signed a contract with the company sales rep on 27 February 2009.  Today, 8 March 2013, I called to cancel.  The customer service rep told me that I had 23 more months to go on my contract and I would have to pay $516 to cancel the contract.  I told her that I only had a 3 year contract.  She said yes, that is correct, and after the 3 years was up, the company automatically renewed my contract again, for another 3 years.  She said I will still be charged $45.95 a month until I pay the additional $516.  This is a total ripoff.  The company did not do anything more to warrant the additional $516.  I will not pay the $516, or the $45.95 monthly.  I told the rep, that as of March 8, 2013, I have cancelled the contract and the company will not receive another penny from me.