Can you please tell me dg7feq:

What is the advantage of using guthaben.de ???
They charge well hidden "transaction fees" of around 5%.

There is http://www.prelado.de. With them the recharge is absolutely without additional fees, at least for the providers i know of. They use the same payment systems and their website can be switched entirely to English?

So why do you recommend guthaben.de? To place an ad? There a dozens of top-up agencies doing it for a surcharge? So compared to prelado, what's the reason to choose guthaben.de?

i only used guthaben.de website so far, the other one (prelado) is even blocked on our company network, dont know why. If they are also good then its nice that you refer to it here.
Thanks for sharing.

I used ladeshop.de to top up my Alditak using a credit card few times when no Aldi shop was close or being out of Germany. Much faster (the amount is credited almost instantly) than a bank transfer which takes days. No additional fees were charged. Don't know whether foreign cards are admitted though.

That didn't work out? Shame :(

Australia is a totally different market with much less competition than Germany sees. So you can't compare that, especially as in Germany AldiTalk is a service provided directly by an subsidirary of the underlying MNO (fomerly eplus, now Telefonica O2) which legally is also the contracting party. Aldi simply has licensed its brand to eplus and sells SIM cards for them. If you expand the legal notes in the footer of AldiTalk's website you will see the following clause stating that the contracting party is eplus:
So you can assume that their tariffs are sustainable.

One problem with prelado.de, though, is that they only accept bank cards issued in Germany. Since this in an international forum, prelado.de is not an option.

Thanks for telling us. I was not aware of that.
This may then be true to other 3rd-party top-up sites like guthaben.de or ladeshop.de too and makes topping up German SIM cards by credit card much harder.

I believe you, because the geo-restriction of credit cards is used in the UK too. It's almost impossible to top up with non-UK issued cards.

But I don't believe you too: prelado.de accepts PayPal too. With special payment systems like PayPal I never had any geo-restriction on any site which accepts PayPal. I don't even think a geo-restriction is possible with PayPal. How should the merchant know, to which source your PayPal account is linked?
So I still think you can use any PayPal account to load German SIM cards on prelado.de.

Is anybody (from outside of Germany) here who has other experiences?

UPDATE: The following has been confirmed by prelado.de

I send them a query by mail. Here is their reply:
Leider können wir aktuell aus Sicherheitsgründen nur Kreditkarten deutscher Banken für das Aufladen des Guthabens akzeptieren. PayPal konnte bisher auch von ausländische Kunden erfolgreich genutzt werden.

Translation: Unfortunately, we can only accept credit cards of German banks for top-ups right now for security reasons. PayPal can be used sucessfully by foreign customers for topping up.

So summing up: German SIM cards are still hard to reload by non-German credit cards. Only Ortel and Lebara offer this option on their website (but may restrict some cards too). 3rd-party reload sites like prelado.de only accept German credit cards.

But there is a loophole: If you want to keep a German SIM card alive and are not in the country (where you can buy vouchers), use PayPal e.g. on www.prelado.de without surcharge. Only for transactions of NON-€ currencies PayPal charges high conversion fees.

It doesn't work with paypal either, when paypal is based on a non-German bank card. I have tried several times. The underlying card has to be German for Prelado to accept the payment.

you need to have positive balance on your paypal account, then it will also work,

Chris