Why is 'fast charging' on Note 5 no longer 'fast' after Android 7.0 update today?

[AC Question]

I updated my AT&T Note 5 to Android 7.0. When all functions returned, I placed the phone on the wireless charger. It said on the pull-down screen it was 'Fast Charging', however, it was not. I tried connecting directly to the wire, and I tried restarting. No fix yet.
How do you uninstall 7.0 to the previous OS?