After a lot of searching, waiting and struggling, I managed to successfully upgrade from 6.0.1 (v10h) to 7.0 (v20t) and then 8.0 (v30a) with the help of a friend by OTA method.
I have TOT firmwares for H820.
1. H82010h (6.0.1)
2. H82020t (Last update of 7.0)
3. H82030a (8.0)
Which firmware you want?
If I got some positive response, I will be posting them on XDA for free for everyone.
Note: All 3 files have been read from my own phone by myself with a professional tool.
So, are you ready??