"Technically classed as" according to whom? First of all, I don't see why the two terms would necessarily be mutually exclusive. More importantly, "cult" is a loaded and strictly derogatory term. No group would ever identify itself as a "cult". This article elaborates:http://www.religioustolerance.org/cults.htm
Satanism is indeed a religion, since we have our own versions of main components that other religions have (dogma, ceremony, symbolism, conduct/ethics code, a central source of official literature, etc.). Here in the US and in many other countries, it is legally recognized as a religion.
We do not, however, share the characteristics that are stereotypical of "cults". The Church of Satan
does NOT demand that members ever even meet each other, does not demand irrelevant sacrifices from one's own personal life (unless it involves illegal activity; we don't condone that), we don't prevent people from leaving if they want to, etc.