Ironically, because phone designs have converged so much and innovation had plateaued, a phone with no branding whatsoever represents a brand in and of itself. Think about it, even the worst, cheapest no-name phones built from old parts in some small Chinese factory have something written on them. The absence of a logo is so unique that it performs the same function, because no one else is doing that. The catch is that it only works if people know this gimmick in advance, but this also applies to brands with textless logos.