I you like have your customers to use GIRO/POSTGIRO for payments

Then you have setup like this

If your only payment methods for customers is GIRO/POSTGIRO, the setup on your BC Company page

You can copy this text below
SE:BANKGIRO

Next add 30 as payment means in Payments Methods at the GIRO payment method

On your Customers add GIRO as Payment Metod

For further informations you go to this link, form the skr.se

https://skr.se/download/18.42336a32177c8ab158d772c8/1616148138445/The%20use%20of%20payment%20means_2.pdf