In general, "double scheme cards" (MC + Maestro on one card) should offer you the option to choose, while at the POS, which scheme should be used; the thing is, the merchant is not required to offer you this question, and there is a "default scheme" on such cards. This means, in cases the merchant does not ask you, the default scheme is chosen, which is usually the one that brings in more fees for the bank/PSP.

And: Depending on the contract between you and your bank, it maybe that you couldn't revoke the "lastschrift", yes.