I am going to do this, but maybe there is more institutions where can I report this scam?
Just report it to the local authority where the parent company operates. You can find their address based on their "about" page.
Papaya was founded in January 2012 and is a fully set up Electronic Money Institution (EMI), headquartered in Malta. Papaya is regulated by the Malta Financial Services Authority (MFSA), the single regulator for financial services in Malta – a growing international financial hub.
The MFSA is the authority that will take action against them. But I'm not sure you won't need a fee to process it, just reconsider that all you want to claim is 50EUR.
I prefer OSS opinion above, leave bad reviews wherever they promote.