Sportingbet Casino - Account closed and winnings confiscated with no justification or proofs

Dear Sir/Madam,

I have been using sportingbet.com for 1 year earning around 2.790€. Few weeks ago, when I tried to withdraw part of my money, I have been asked to provide the following documentation in order to verify my account and proceed with the payout.

"1 - A color copy of an Identification Document (Passport, National ID card or Driver’s License).
2 - A color copy of a utility bill or bank statement dated in the last three months, showing your name and address.
3 - A color photo of your ID held next to your face
4 - Proof of ownership of your Moneybookers account (please take a screenshot whilst logged into your account so we can see the account details)"

After I provided the whole documentations, my account has been closed without any explanation. They would only send back the money of my first deposit (400€) withholding my winning (2790€). Please find below the last email I have received from them:

"Dear Anna,
Thank you for contacting Sportingbet Customer Support,
Please be advised this has now been sent to our finance team to request the 400 Euros back to your skrill account.
If you have any questions or require any further assistance, please don’t hesitate to contact us further, we're always happy to help.
Kind Regards,
Troy"

I have not done anything wrong and I am more than pleased to provide any further documentations. I am sure there must have been some mistake in their verification process but they do not reply to my email and it seems they have just stolen my money without further explanation.
Could you help me with this?

Thanks in advance for your collaboration

Cheers

Anna