In my experience, there's always some trigger in the fine print that functions as opting in. In the instant case, if the salesman had once gotten you to say 'yes' over the phone, or if you had received and used the "no strings attached" card, or . . .

Well, I certainly said "no" a lot over the phone. And I think I may have actually already received the "offer" and thrown the "free gas" card away because the verbiage smelled like a "use this and enter a contract" offer. I specifically asked the sales guy about whether the "free" gas card came with strings attached because I was recalling the card I got (although I wasn't connecting it with this phone call, since the caller said I'd be receiving something in the future). He said, no, no strings attached, using the card wouldn't tie me into anything. Of course, in his universe, what tied me into the contract was the absence of opting out, so I suspect he was technically sincere in claiming that using the card wouldn't affect anything.

But I still find it hard to believe that this is legal.