Talk:Germany/@comment-146.21.1.22-20150806075003/@comment-24682153-20150806081004

That's right. In the article it's not specified for prelado.de but it is valid for all top-ups by vouchers: "You can use Telekom vouchers for Congstar and ja!/Penny mobil, Vodafone vouchers for Fyve and Edeka, Eplus vouchers for Aldi/Medion, ortel and Whatsapp and O2 vouchers for Netzclub. Lidl and Fonic vouchers are interchangeable, but not with O2. For blau, Klarmobil, Lycamobile and Lebara, you need special vouchers which are less widely distributed" 

So if you are using 3rd party sites to top up and your provider is not listed, with many providers you can use their MNOs instead.