Chevron Pump Theft Lake Placid Florida

I use Chevron where I spend my summers.  I scoot down to Florida for the winter and drive an extra 10 miles one way to use Chevron gas.  My mechanic tells me its the best for my car.  Have noticed over time that the amount of money I've been prepaying doesn't seem to reflect where it should on my gas gauge.  I've been writing it off thinking it was just my imagination.  Well on 11/08/2016 I bought a 5 gallon gas container and went to fill it up.  I prepaid $40, the rest would go in my gas tank.  It took 5.6 gallons, according to the pump meter, to fill up my 5 gallon gas can.  How can that be?  It can't!  It was then I knew I had been getting ripped off all along.  I told the workers there - no one seemed to care.  I contacted Chevron via email on its contact form.  I am furious.  How many other people have been getting ripped off?  WHO gets the extra money - Chevron or the owners of the station?  How many other other people have unknowingly been getting ripped off? Well ... they've been getting away with it and there doesn't seem to be anything I can do about it but complain.