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

Then you have setup like this

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

Else create a new bank account for this, and add this to the linie on the Payment Methods, see below

You can copy this text below
SE:BANKGIRO

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

On the Customer Card add GIRO as Payment Metod

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

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