Unknown bank transaction from Apple Pay

It is your bank that approved the transaction, that is not done by Apple Pay. Apple Pay simply provides a unique one time use code so your account numbers are not used for a purchase. You dispute a charge on your card the same way whether you use Apple Pay or not.

Not sure about your region, but in the US, a bank must investigate a transaction when you have formally disputed the charge. You should always attempt to contact the merchant first, because most of the time the charges are legitimate and you are not able to recognize the purchase by the description. If you have no luck with the merchant or with your bank, then check your local government for the steps to take that would force the bank to investigate. In the US it is the CFPB, but since you are dealing with Euro's I would suspect you have a similar agency.

Is the transaction from Apple? It doesn’t appear so. Contact the merchant then the card issuer.