A Pac-Man-style online game that charged unwitting customers up to £4.50 a week has led to a £45,000 fine for its Cyprus-based service provider.
Regulator PhonepayPlus said it had fined Nobinet and ordered refunds over the "misleading" Gameztour and Playneto games.
The regulator said Facebook and Tumblr users were lured into the games by advertisements promising to reveal who had viewed their profiles.
When clicked on, the adverts re-posted themselves on to the user's wall and took them to the Pac-Man-style game.
Users were asked to enter their phone numbers to start the game, with the promise of high-value prizes, but several reported that they had not realised they were signing up for subscriptions costing up to £4.50 a week.
PhonepayPlus said it received eight complaints about the games, but urged anyone affected to come forward.
PhonepayPlus spokesman Patrick Guthrie said: "Consumers were tricked into signing up for this service by misleading digital marketing.
"Most affiliate marketing services follow the rules, but this case should be a warning to consumers to take care following adverts that then require them to enter their phone number online.