I would probably return the money, I don't need to steal. But having your balance stole? No, this is a unacceptable way of doing this, and that's not the balance, they even let me play it and so took my winnings as well.
Then what are you complaining about? You wanted to return the money, so you deposited to return the money. You have no case. They couldn't steal anything because:
1. It's their money
2. You just said that you wanted to return it
Well said mate, OP can not claim the money in this situation as he admitted to return it. It is also wrong to say that nitrogen has stolen the money as it belongs to them so Op should given up on his claim but they should look into his negative balance thing.
Yes, I can claim my new deposit and my winnings. Well, I made a new deposit with them, if you steal back your money that is still stealing. You can't do the right thing in wrong way.
They should have advised me prior my deposit, the least they could do is to block my account just after the deposit, so I would no play with this money into their sportsbook, you can't allow someone to play, win and after it just steal their balance, no matter what happened in the past.