Assuming you contacted fi because that's who you have as a carrier then this is what you install, or if you live in Canada:
8.0.0 (OPR1.170623.026, Sep 2017, Fi/Canada)
If you have TMobile , sprint, etc. Then you'll use this:
8.0.0 (OPR3.170623.007, Sep 2017)
I see what you mean about the OPR...