If you bought SAM CAST, you bought the completely wrong software. SAM Cast is a standalone encoder for use with Winamp or some other playback software.
You are probably talking about SAM Broadcaster Plus though, which is the premium version of SAM Broadcaster Lite.
SAM Broadcaster Lite and SAM Broadcaster Plus can be used with SpacialNet or Cheapeststream subscription, BUT NOT with any other generic Streamhost.
If you have your own Shoutcast Server or Stream hosting from a company that is NOT a subsidiary of Spacial, you need to buy the SAM Broadcaster PRO version. This is clearly stated on the Features page. (Shoutcast and Windows Media via SpacialNet ONLY!)
SAM Broadcaster Pro allows you to broadcast through your own stream online. If you want to broadcast terrestrial signals as well, you need th SAM Broadcaster Studio version.
Spacial gives you a demo version of the software for free, so you can try out if the software suits your needs BEFORE YOU pay any money as they don't offer a refund policy!
You should get in touch with Support via the Help Desk immediately. We cannot guarantee anything, but as you are not the first person to mistake the cheaper Plus version bundle for the full-featured SAM Broadcaster, I guess they will allow you to upgrade by paying only the differnce. A full refund is unlikely though.
You can create a ticket over here:http://support.spacial.com/home
Also: I don't see any SAM Broadcaster version being sold for only 100$ on the Spacial Homepage. The Uprgade from SAM Broadcaster PRO 4 to SAM Broadcaster PRO 2013 was 99$, but any retail version of SAM Broadcaster starts at 149$ for the SAM Broadcaster PLUS version or 299$ for the SAM Broadcaster PRO!