You can try, but in Germany it is almost impossible to make a chargeback for casinos with reference to the changed transactions.
Most banks block them because Mastercard's chargeback guide states that transactions related to gambling are not eligible for chargeback, so it doesn't matter whether the MCC has been modified.
If you submit a chargeback because you did not receive the service, the banks will ask for receipts, which you cannot submit because there are no receipts.
I even lost in one chargeback case because the merchant presented fake invoices, so be prepared for anything!
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