How to cancel BizeRat magazine once and for all?

After purchasing my contact lens, i received an email if i complete an survey they would allow me to pick four magazines for free with $2 shipping fee each for an entire year. I know about tat if I don't cancel it in time, there will be some risky consequences. So i emailed them, talked to an operator, and even went on a website to cancel the renewal. But still, they still find a way to charge me despite all the effort I putted into cancelling it...Currently they are probably still sending magazines to the house that I no longer live in, and it feels like I'm trapped cuz they have my credit card # and will charge me as often as they want. There is also no chance that i will learn about them charging me because i returned many items bought from credit, so my credit bills are automatically pay off by itself...how do i escape this scamm?