I'm from Croatia but I don't send money abroad, I only use credit cards and banks locally. As far as I can see from our local banks' websites, they implement SEPA standards. There must be some sort of misunderstanding or error.

Perhaps is because it's a payment to an OBRT account?

Banking in Croatia is like UK banking 40 years ago, or at least it is with Erste. Charged even just to have the account.

They even charge me to send me an email to tell me I logged in to the online banking.

They charge for pretty much everything, even for running your bank account. But now they will not be allowed by law to charge you "bank account operating cost fees" for bank accounts that are used for receiving salary and/or pension.