I just used a promotion from Wintomato, without problems by the way, all ok, but I was going to do it with BTC for the deposit, but it turns out that its fee is 0.0004 BTC (min withdraw amount 15$) which is quite high, given the conditions of the mempool, in fact I think that If I had done it there, the winnings for the free spins were about $15, which would be really bad for someone who does not review, which is the great utility of their OP, now I double check, I review your OP and then the casino  in that sense I can confirm that winz maintains its fee 0 + the bitcoin network fee.