Shameless self advertisement incoming...
It's not really alternate history, or even Orwellian style dystopian, but my story TechNOIR is set in a dystopian cyberpunk world where megacorps rule everything. The story doesn't really focus much on that though, but I'm gonna be writing more stories set in that universe in the future that do, so look out for those. Until then, you can feed your dystopian crave with that story.
I do know that there's actual Orwellian style dystopian stories hanging around (and there's a 1984 fanfic, but IIRC it sucked), but until 3J comes back from fighting trolls and warrior cats in the seventh dimension and implements the search by tag feature, you're gonna have to sift through the stories individually looking for that tag.