As far as I know that's not the case. I am not an expert on slot games, but I noticed that several big online casinos all use the same slot games. The games are developed by third parties and have a fixed return to player ratio. With the help of Google we can find RTP for the slot game before playing. The casino itself has no real impact on the game, they just provide the platform and customers for it. Also the casinos don't need to change the RTP, because all the slots are already profitable for the casino. The longer we play the closer we will get to the expected value, which is negative for us gamblers. Did you have a streak of bad luck?