With respect, you didnt 'get robbed'.
Web Assist announced some months ago that they were ceasing support for all languages apart from PHP, and the system requirements for DFP2 do not mention ASP.
I'd suggest you contact WA to see if they can sort you out with a refund given your 'misunderstanding'.
The DMXZone extensions work fairly well, but support in my experience is virtually non existant.