A little more information might be helpful. I do not play on Carbon so I do not know what these "free SnG steps" you speak of are. I am guessing you get to play a free SnG and as you make it up the levels/steps eventually you win money. AFAIK there is nothing like that on Pokerstars
, Full Tilt, Players Only
, or Bodog, and I would guess Cake as well.