Coral Casino - Excluded account no refund

Created a new account with coral without an issue, deposited £200. Asked the casino before depositing further if I had previously had an account as I thought I might have had but it was closed etc, hence being able to open a new one. Told by coral I was previously excluded and new account was closed. They accused me of circumventing their rules by using new details! I used the same name, date of birth, and email, which they claimed was different because I accidentally used a capital G for gmail and the old account was lowercase g. Ridiculous that a large group like that can be fooled by a case mistake in an email. Also I've moved house in the last few years which meant their system could not find me. Requested a refund as I shouldn't have been able to open a new account and they refused, said it was my responsibility not to open a new account. Surely it's their responsibility to make reasonable checks against their database?