After nearly 20 years of going to PNE and parking at the Jet Center and generally getting good service we were solidly let down last Wednesday June 20th. We flew our Citation on the hottest day in Philadelphia this year (afternoon temps 97F) and arrived well before 9AM and immediately requested a GPU between the hour of 2PM and 3PM to run the air conditioner to cool the cabin. My first officer was told repeatedly "no problem" -- Just before 2PM he was told "no GPU available, it has been taken by another aircraft" -- OK so the cabin was hot, but the biggest let down was on fueling. We requested jet fuel with prist additive. Prist prevents fuel icing at high altitude. When my first officer watched the fueling process he found he no prist was being added. He immediately stopped the fueling process and asked to see the manager. It was then discovered the prist container was empty, after some delay the prist was added manually per first officer's calculation of fuel volume on board - A total fiasco that could have had serious consequences! I called the Jet Center the next day (6/21) but was told "no manager on duty" I told story and was promised a call that never came. I am very disappointed and will not return to that FBO - Amir Novini, Commercial, CE550 Captain.