Actually, only one paragraph in the article matters regarding the entire reverse lookup at directory assistance: If you can do well without your own phone number landing in the databases of information brokers and being "reverse-translated", you can lodge an objection at 01375/103300. This works automatically, quickly and conveniently. Important: Be sure to use the line you want to exclude when calling, as the phone number is determined automatically and not requested.
So simply call from the appropriate line, listen, wait for the signal tone and pay 12 cents. Even though I find it absurd that I have to explicitly object to something I never agreed to in the first place ...
At WDR.de you can find the original article.