And you can use that to buy goods online? Direct debit is usually used for recurrent billing. In Portugal there's a way to use a similar system for online purchases by generating a code that you then have to use in an ATM or online banking. It makes for a pretty poor customer experience when purchasing and I doubt it's actually cheaper these days than debit/credit payment processing.

Amazon certainly accepts payments that way. And many other online retailers offer GiroPay, which I think is a payment method based on SEPA Credit Transfer. I don't know about the cost structure of that one.