Fortaleza de Belogradchik autoguiada

DO NOT USE THIS SITE. I booked a self-guided tour for the Belogradchik Fortress, I spent €19 per person (there were 7 of us), and just think, only the day before the activity was I told via email with a receipt that the €19 basically included nothing since I still had to pay €4 to enter. Well, disheartened, once I arrived there they told me that the "viator" site does not work with them and that I had to pay €8 per person (full price, therefore). Therefore, those €19 per person, €133 total, were completely useless because they did not guarantee me anything, admission or anything else, and furthermore, a site that sells you an activity but then turns out not to be a partner of the physical operators working there is a total scam. Shame on you, I will never book anything with viator again, they are not serious and they always respond to my emails with the same thing, that is, that they told me (one day in advance) that I still had to pay for the ticket. I then replied that they were not cooperating with the activity and that I paid €8 instead of €4, so the booking with Viator was useless… but I received no response. I repeat, shame, but the story does not end here anyway; I have been asking for a refund for days and they are ignoring me, but I do not intend to let them win.