Advertising Bill

We were just called today and were told that we owe almost $1500 for advertising with Yellow Pages Online.  The problem is that they are saying that I said yes to a four year contract.  As I am reviewing what has been said on this site...I believe I did agree to a one year contract back in 2008.  I have not been billed for any advertising.  When I told them that I hadn't received any bill from them they read me an inaccurate address and said that was the address I verified back in 2008.  I told them I would not have verified a wrong address.  I asked to speak with a manager and to have proof that I signed up for a four year service.  I was told it would cost me an additional $250 to get proof of verification.  How do I fight this?  I need help.  Thank you.