Completely agree that Fox rental car is among the worst of the rental car options. I'm not sure it's Southwest's job to filter what companies are are available to their customers, but I guess if enough people informed Southwest of the horrible service one of their partner was offering they might do something about it. I, like you, have had a bad experience with Fox and other companies and just use it as a personal learning experience to never rent from them again.
A tip for anyone renting cars, whatever agency you rent from, enroll in their free membership that lets you utilize a priority line or skip the counter all together. Those rental counters never have enough staff. If you really want to have great service, check out Silvercar, it's like night and day compared to any other rental agency and often not that much more expensive.
