Use other charging providers alongside Mercedes me

I have an EQS as well as a Hyundai Kona and therefore also an ENBW+ special tariff. In general I charge the EQS to IONITY. But sometimes there is no IONITY column nearby. Now I have found that many columns in Mercedes cost me 0,90 € instead of 0,52 € at ENBW+ per kilowatt hour. The charging of the EQS by means of Mobility plus App was also problem-free when you first found the correct name of the column. Now the problem: also the Aral Pulse columns are at the moment significantly cheaper at EnBW. So I started the charging process by means of an app. But then I saw that the charging process was billed directly with Mercedes thanks to the plug-n-charge. How can you prevent this? Does someone know a workaround?