Hi, sorry for the delay in coming back to you here. Looking at the basic facts of this case the player did break the terms and conditions of the casino.
The term that covers this can be found here...http://www.manhattanslots.com/Terms.aspx under the section Players Representation and Warranties.
Term 20 covers this exact scenario...
20. Use of a credit card not registered to the Player will be deemed fraudulent and will result in winnings being voided, unless previously confirmed in writing by MS.
At no point in the lead up to this was the use of credit cards in other people’s names raised, discussed or confirmed in writing. The risk of using other peoples cards is obvious and there are alternative options for two players to play from the same household. For this to happen both players must, in advance confirm their identity and provide the relevant documents to the casino to verify both users on the same account. Alternatively, with the approval of the casino two accounts could be opened with only one account being able to claim the welcome bonus. Obtaining an additional card on the same bank account/credit card may also be an option. A further option would be to open up another account in another casino in the group and continue to play separately without any restrictions on the bonus or worry about terms.
If, as a player you are unsure of the best way to create an account so more than one user can be active, it is essential that you contact our support team who will give you the correct information on how to go about it. They are available 24/7 365 days a year and can assist you in any situation.
We are sorry that your first experience didn't go as planned, we are a fair casino and we stick by the terms and conditions that our casino offers. Unfortunately, on this occasion I am unable to do anything to overturn the decision of the casino this time.