Well, saying that you havent received any service from them is not true If you have received the deposit into your casino account. They have acted as a payment processor/payment gateway to the casino. That is not illegal per se. So if the casino has received your payment, you have received their (the payment gateways) service. And by saying otherwise to your bank, you are attempting fraud (försök till bedrägeri).
Misclassification of MCC codes are, as I understand it, not illegal either. Yes it is against Mastercard and VISAs policies and terms, and can lead to suspension and fees imposed by VISA/Mastercard to the merchant. It is also in general skechy and if it would be thorougfully invested it often has connection to money laundering (which is illegal). But I doubt misclassification of MCC codes is an actual crime.
Automatic translation: