Dealmax Signed me up to a shopping discount program without my knowledge Internet

I didn't notice that Dealmax was debiting my credit card account for $19.95 until it had been going on for 7 months. When I called to complain, they said it didn't matter that it had been don without my knowing. They said I would be credited for one payment. I'm convinced that my credit card number, my address, and my email address was obtained from a previous internet purchase. Although there are 4 reports of this scam on the internet going back to Jan, 08, Chase Mastercard insists that they will not help me.

William
Roxbury, Connecticut
U.S.A.