It reminds me more of the book catalogues. 5 books for a pound or something as a joining perk, but you then had to buy a book a month for 6 months or they would automatically sell you the default book etc.
I never thought that was a shady business model, per se, and whilst it wasn't entirely intuitive how they worked to a 14 year old, I blamed myself for screwing up by joining- not the company.
As a child my father had pointed out to me that those book offers (in the UK at least) were only for adults (18 and over). So I used to fill in the form without ticking the 'I'm and adult' box, and see if they sent me the books. Most did, though as I was a minor they had no recourse to ask for payment. If only you'd contacted them and told them you were too young to sign a contract!
When books you didn't order start showing up in the mailbox, you pretty quickly catch on to what's happening. Charges that just show up on your credit card statement are a lot less obvious to most people.