Sorry but it sounds like a bad stealership strikes again! I always continue to fill mine after the nozzle stops as it holds another 4+ gallons and I get 500+ miles per tank...as every car should! Anyway, when I first got my car (used w/ 16k miles) I thought something was wrong with the gas tank or fill pipe because it would only hold like 16 gallons. One day I just kept filling it, albeit slower than full speed, but I filled it right up to when there was gas in the fill port. All was fine and I've continued to do that for the last 2 years and past 40k+ miles with no issues. Don't know what to tell you but I'm sorry you're getting the runaround.
2014 SXL, only mods are after market rims due to recall.