Did you put all 250 on one bet? Did you make any other bets? How did you deposit the funds?
From what I understood is that OP made a deposit via card, placed one bet, withdrew $450 and SB seized all remaining funds.
You mean like credit/debit card? Not sure if that's what the OP meant. So if it was a single winning yolo bet at 3.74, there would have been ~900 euros total in the account.
You gotta love how there are always 4 accounts mentioned in the customer support e-mail. Amazing totally not coincidence.