You need to provide more details. Did they charge you taxes after midnight on 7/22? If they charged you taxes prior to that (no matter when the flight was for) the tax was neither "unauthorized" nor "illegally collected". A lot of airlines may have been charging the taxes for a few hours after midnight (for example if their systems were based on the West Coast, even though it was after midnight on the East Coast, the system may have still recognized the day as 7/22).
If they just charged $20 or so more than they were charging the previous day, then they were being like 95% of the other airlines out there by increasing their prices by the exact amount of the expired tax. Though "bogus" this behavior was not illegal; one could choose to only fly airlines that did not increase fares but then one would be stuck on Spirit.