According to the annual report (https://www.zaftda.de/tb-bundeslaender/berlin/695-tb-lfd-ber...), N26 used to add all former customers to a black list, which is not allowed if there is no suspicion against them.

>>Eine schwarze Liste für ehemalige Kundinnen und Kunden, gegen die keine Verdachtsmomente bestehen, ist rechtswidrig.

translated with deepl: >>A blacklist for former customers against whom there is no suspicion is unlawful.