Assuming you gamble on a mid to high-rated gambling website and you won big but they refuse to pay up, what and what are the legal way to make sure that the platform pays up your money?
The first thing you need to remember is that for large scale gambling you must be gambling at a licensed casino site. Then if it happens as you mentioned in your post then immediately report it to the licensing company for that casino with all valid proof. Then they can help you. And if there is any ANN in this forum about that casino then don't feel free to open a scam case against that site. It might also help you in some way to get your fair