Private stamp Topical issues sold as genuine

[aortz]

Several stamp sellers on eBay are offering "very nice" topical stamps from mainly African countries but these issues are of private origine.   It seems nobody has reported this to eBay and it is just encouraging the practice.  Collectors will end up having beautiful collections of completely unworthy stamps.   How can this be escalated to eBay to clearly state that such items are not legitimate and forbid to sell?