Did you pay duty fee and/or import fees for POV shipping as a contractor to an overseas post?

I am being told I need to pay about $511 in import dity fees for my POV shipping cost on topof the $3050 I alread paid for shipping it. I am told that under the SOFA agreement my ILS terms allow me to bypass any such fees and VAT tax per my status as a technical rep contractor serving a US military/government interest overseas.