Landed at KSBA a few years ago on a commercial xc requirement flight. Hit the self serve fuel, then taxi'd over to Atlantic as I thought I'd go grab some lunch real quick. Nobody out to park me, so I parked as far out as I could so as to not be in the way. Walked into the FBO and was greeted with a request for $20 or $25 parking fee. Told her no thanks, I'm leaving. Took off right away and never heard from them again. I know I didn't buy fuel from them, but I thought it was pretty crappy. Ramp was empty, parked myself way out in the middle of nowhere, walked in, didn't bother anybody.
Nowadays, I avoid Atlantic just as a matter of principle. I probably shouldn't, because they never sent me a bill but I still do. The entire encounter could have made a loyal customer, instead it left a sour taste.
Just buy fuel from whoever and you won't have to pay their "trespass fee."