Readers Source trying to get money for magazines i didn't order from them Oakley, California

First of all, I did not order magazines from this company. I started with the National Magazine co. I agreed to pay 5 payments of $33.64. The next thing i know, I'm going to be billed $49.98 for 24 months for there magazines. Right then I changed my credit card #.

This was in March,2009. In may 2009 they send me a past due notice. In June,2009 I received a notice to thank me for my call to cancel my magazine service. The order was cancelled.  Now I receive calls about my money owed for these magazines. Today, April 8,2010 I received kind of a threatning call to pay $1100.00 or it's going to the collectors.

 The only magazines I'm getting are the ones i ordered from the first company and they are paid for. Can some one give me some advice on this?