coinbase.io
coinzone.inkAll of them let users sign up first and use promo code to redeem some quantities of bitcoin, which amounts to thousands of dollars. When it comes to the time to withdraw, they ask the users to verify the payment by sending amount of cryptos to the website system account. DO NOT GET CHEATED ON!
Its a very old method of scamming people; they usually target newbies because they know how this thing works and they are greedy. Any website that asks for funds before you are allowed to withdraw is an outright scam. They first did it in a casino, then after getting exposed in the gambling community, they targeted the traders by launching their own exchange, but the scheme is still the same.
If you are not updated on the various methods of these scammers, you might get victimized, so be aware.